hm**-
UCTION TO THE STUDY
NATURAL  HISTORY,
IN A SERIES OF LECTURES DELIVERED IN THE HALL OF THE COLLEGE ^^«.
     OF PHYSICIANS AND SURGEONS, NEW YORK.
ILLUSTRATED WITH NUMEROUS ENGRAVINGS.
A BIOGRAPHICAL NOTICE OF THE AUTHOR.
?**■
BY PROFESSOR AGASSIZ.    gjjgj
         NEW-YORK:
GREELEY & MCELRATH, TRIBUNE BUILDINGS.
1847. 
T
X 
AN
INTRODUCTION TO THE STUDY
NATURAL  HISTORY,
IN A SERIES OF LECTURES DELIVERED IN THE HALL OF THE COLLEGE OF
       PHYSICIANS AND SURGEONS, NEW-YORK.
                    /

   BY PROFESSOR AGASSIZ.
ILLUSTRATED WITH NUMEROUS ENGRAVINGS.
A BIOGRAPHICAL NOTICE OF THE AUTHOR.
„v
        NE\V-YORK:
GREELEY & MCELRATH, TRIBUNE BUILDINGS.
1847. 
PREFACE.
  In accordance with the request of the Faculty of the College of Physicians and Surgeons, Professor
Agassiz delivered, in  the Hall of that  institution, during the months of October and November of the
present year,  a series  of twelve Lectures on the  various orders of  animals.  The celebrity of the
Lecturer and  the intrinsic interest and importance of the subject, attracted very large and attentive
auditories.  Indeed, the degree of attention excited by these admirable discourses manifested, in a
very striking manner,  the greatly increasing interest with which the popular mind is now directing
itself to the investigation of scientific subjects.
  Full reporta  of these Lectures were given in the columns of the " New York Tribune," and abundant
evidence was afforded of the high appreciation with which they were received by the public.  They are
now collected together;  and having been carefully prepared for this publication in a permanent form, it
is believed that they will prove acceptable to all who take an interest in the study of  a department of
Science which is daily becoming invested with fresh attractions.  The young beginner and  the  more
advanced student of Natural History will both  derive essential aid from the study of these discourses;
as, while teaching first principles in an eminently lucid  and comprehensive style, the Lecturer commu-
nicates also the results of the most recent and elaborate investigations in the latest discovered fields of
philosophical inquiry.
  The Lectures, with  the exception of one or two, were reported by Dr. Houston,  Stenographer to the
Senate of the  United  States, and he has  succeeded in giving them with literal accuracy, so as to pre-
serve the characteristic style of the Lecturer.  The few Lectures not reported by that gentleman, were
subjected to a  careful  revision.   Of the  engravings  it is only necessary to say that they were rapidly
sketched from the black-board during the delivery of the Lectures, by Mr. Brydges, with perfect accuracy,
and will be found to contribute essentially to the elucidation of the subjects discussed in the Lectures.
Very many of the illustrations  are altogether original, and cannot be met with in any of the treatises on
Natural History heretofore published.

     New-York, December 10, 1847. 
BIOGRAPHICAL   NOTICE  OF  PROF.  AGASSIZ.
  Louis Agassiz  was born on the 28th of May, 1807, in  a village  of the Canton of Fribourg, Swit
lerland, called  Mottier.  His father was a clergyman, a profession  to which his progenitors for five
generations had been devoted.  He received the first rudiments of t,cholastic education at the Gymna-
sium of  Bienne, where he passed several years, principally in studying the ancient languages. His
passion for Natural History appeared  during this period, and his vacations at home were employed in
making  collections.   His father having removed to a parish on the  Lake of Neufchatel, he made fishes
an object of especial study.  He went with the fishermen on their excursions, and often, with a line in
his hand, passed whole days on the  Lake.  He soon discovered how defective Natural Hi8tory was in
this department, and resolved to make good the deficiency.
  Having completed his studies at school, his father wished him to become a clergyman, but his natural
bent was too strong to be resisted.  He accordingly commenced the study of Medicine, as being mosj
nearly connected with his favorite pursuits.  At the Academy of Zurich he received great assistance in
his Zoological  investigations from the well-known Professor Schinz.  Afterward he  studied Anatomy
at  Heidelberg, under the  celebrated  Tiedemann, until, attracted by the remarkable body of savans
collected at Munich, he resorted  thither to continue his studies  Here  he passed four years, rather
as  an associate in the private studies of the Professors  of the University than as  a  student  under
their instruction.  He also  collected around him a knot of  young men of kindred spirit  with himself,
for the discussion of scientific subjects, and into this assembly, which was  called the " Little Academy,''
even the Professors were drawn.
  At this time Agassiz made his first appearance  as an  author, and in the most honorable manner.
Martins, one of the  Professors at Munich, was occupied in preparing his great work on the Natural
History of Brazil.  To Agassiz he confided the department of Ichthyology; this portion formed a folio
volume, in Latin, with plates,  and at once established the reputation of the young Naturalist.
  His parents,  who had long been dissatisfied with  the devotion of their  son to Natural History, which
withdrew  him  almost wholly from his medical studies, now cut off the allqwance on which he had
depended for a living. In this emergency  he fell back upon his own resourcea.  He exhibited to the
bookseller Cotta the material  he had collected for a work upon Fresh-water Fishes, and  obtained from
him the means of completing that work.  At the same time he returned to Medicine, in order to regain
the favor of his parents, and with so much success that he shortly after obtained the degree  of Doctor.
Subsequent to  this he passed another examination, and received the degree of Doctor of Philosophy.
  Having been restored to his  former  relations with his  parents, he received from them permission
to visit Vienna in  order  to  complete  his medical studies.   He did not, however, neglect his favorite
pursuits, but, as before, occupied a great part of his time with Ichthyology, and especially with  the
department of Fossils.  On  his return home, he obtained  from a neighboring clergyman the means of
visiting Paris.  There he became  intimate with Cuvier, who even resigned to him a work  on Fishes
which he  had  long  designed, and for which  he had made extensive preparations—so high was his
estimate of the gifts  and learning of the young man.  He remained with Cuvier until his death in 1832,
when he returned to Switzerland and became Professor of Natural History in the College of Neufchatel.
  Before he had passed the  age  of thirty-four, Agassiz had been made a member of every scientific
academy in Europe.  Many universities invited him to become one among their Professors; and the
cities of Edinburgh and Dublin, in both of which he received the degree  of LL.D. enrolled him  in the
number of their citizens.  His personal influence induced several persons of distinction to engage in the
study of Natural History; among others, Sir Philip Egerton  and Lord Enniskillen, whose collections are
known to all paleontologists.
  The reputation and influence of M. Agassiz have  rendered the little town of Neufchatel a nursery of
Bcience,  resorted to from all parts of Europe; and on his recommendation a young pupil of his, Dr. 
4
Biographical Notice of Prof. Agassiz.
Tschudi, who has since become known by his work on Peru, was dispatched on a voyage round the
world, to collect objects of Natural History.
  In order to confirm the Glacial Tneory which has made bis name so famous, M. Agassiz, after having
visited in succession most of the glaciers, fixed his headquarters at the glacier of the Aars, whither he
went with his friends to pass his summer vacation for eight years consecutively; at first with no shelter
except a large  boulder  lying on the middle of the glacier, which soon became famous under the name
of the Hotel des Neufchatelois.  Here he  prosecuted the long series of researches which have since
obtained so much celebrity in the scientific world.
  Occupied with these investigations and with his regular duties, Prof. Agassiz remained at Neufchatel
until his visit to this country.  This visit was undertaken at the double instance of the King of Prussia,
who charged him with a scientific exploration of America, and of the Lowell Institute in Boston, before
which he was invited to deliver a Course of Lectures  Since his arrival he has been offered a Profes-
sorship of Zoology  and Geology in Harvard College which he has accepted on condition of being
released from his engagement with the King of Prussia.
  Professor Agassiz is personally a man of very striking and prepossessing appearance.  He is tall, and
formed with as much strength as  elegance,  with a rather fl. rid  complexion and dark  hair.  In  hit
manner and bearing there is a singular grace and  benignity.
  His principal  work is on Fossil Fishes, in five folio volumes, with an atlas of plates.  It is dedicated
to Alexander von Humboldt, and has a very high and extensive reputation.   He has also written on
the Fossil Echinodemata of Switzerland,  on  Fossil Molluscs,  on the Fresh-water Fishes of Central
Europe, on the  Glaciers, and on other subjecta.
  The rapidity with which these works have  appeared, and the research and learning which they all
display, would be inexplicable had no other hand than that of their distinguished author been concerned
in their production    In 1837, M. Agassiz associated  with himself a young  Naturalist, M.  Desor, with
whose valuable  assistance his labors have since been prosecuted.   By this means much more has been
accomplished for Science and the world than could  have been done by any single individual,  however
highly endowed. 
THE    ANIMAL    KINGDOM.
                           INTRODUCTORY  LECTURE.

Natural History—Its Study and the Lights in which it may and should be viewed....Man may expect fully to under-
   stand Nature.... Man's Body similar to the Bodies of Animals—The Cause....The Varied Types of Nature—Aston-
   ishing Variety of Animals—difficulty of at first perceiving any order in them... .The Star-Fish---The Corals.....The
   Jelly-fish.....Clams, Worms, Spiders, Crocodiles, Bats—Their great apparent Dissimilarity and yet many of them
   of the same type—The Lobster, the Spider and the Butterfly—The Cuttle-fish, the Snail and the  Clam all allied—
   The Coral and the Jelly-fish... .Soft Animals and their Power of Contraction___The respective Nervous Systems
   of the different Types of Animals___Origin of the applied terms, Articulata,Vertebrata, Radiata andMollusca....
   The different Setsof Organs in these different Animals.
  Dr. A. H. Stevens introduced the lecturer to the
assemblage in a few complimentary remarks.
  Prof. Agassiz then presented himself to the au-
dience, and,  in a singularly agreeable voice and
marked foreign accent,  delivered  the following
Lecture:
  Ladies and Gentlemen:  Having  to address
you in a foreign tongue, I must first apologize for
the deficiency of my language.   Happily, however,
Natural History has an interest entirely apart from
the form in which the subject is presented to the
student.  The  investigation of objects of Natural
History does not need the aid of rhetoric to invest
it with attractive charms ; and the mind may trace
these phenomena even without putting them into
a definite form, and, therefore, the mode of expres-
sion employed in conveying the results of such in-
quiries is  not so important as  it would be in a lit-
erary work.   I shall do all in my power to make up
for the deficiency of my power of language, by the
interest directly derived from the  subject itself.—
(Applause.)
  Natural History may be studied in very different
points of view.  Some may consider it as a source
of information for useful  purposes.  The wealth of
States depends frequently on the knowledge ac-
quired by individuals of the structure  of the soil.
The working of mines has become an actual busi-
ness  since Geology as a science  has given Us the
key to the investigation of the deeper  regions un-
der the surface of the ground. Many trades de-
  Send on the knowledge of certain phenomena of
  ature. Even Navigation is the result of scientific
investigation and discovery ; and, at this time par-
ticularly,  the vastly increased  facilities of frequent
intercourse between nations have been the result of
the recent progreas of natural  science—of physical
Bcience especially.   Thus, though viewed in this
strictly utilitarian aspect  a  sufficient inducement
may  be  furnished  for the  study of  Nature and
of  the  objects of Natural  History in particular,
the subject is yet to be regarded from  a more ele-
vated point of view.  It is not enough for a philo-
sophical mind to know the natural phenomena.  It
may be enough to know some isolated phenomena in
order to derive important aid in the arts, but  to the
philosopher such superficial acquaintance with Na-
ture is not sufficient.  He wants to understand Na-
ture. He is not satisfied with the knowledge of
isolated phenomena.
  When I say that  the  philosopher desires to un-
derstand Nature, 1  will perhaps better explain my
meaning by an example.  When we enter on the
study of an  author  we may begin  at a very low
stage.  With one of the classic Poets of antiquity,
for example, we may begin by translating sentence
by sentence, with great difficulty, and in this ws.y
we may go through the most beautiful language of
ancient poetry.   But would it by any means follow
because we  have thus spelled over  the pages
of Homer, that we understand him?  Another and
a higher sort of mental process is requisite to en-
able us to know, to understand, that sublime author.
It is only when  we have become acquainted with
the condition of human society in that age—the  ri-
valry which existed between the nations of Asia
and  Greece—and the mythology  of that remote
time,  that  our sympathies  approach the level of
the poet's work and our hearts  own the influence
of the poet's spirit.
  So it is with  the study of Nature.  We  may
know by their name a great  many animals.  We
may be able to  indicate with accuracy the  charac-
teristic  differences  between the various tribes of
animals.  We  may  be able to distinguish the
treea  in our foreats and the plants  cultivated in
our gardens; nay,  we  may  know any  isolated
plant that flourishes upon the surface of our globe,
and yet we may after all know nothing of the plan
of creation.   There is a higher point of view from
which we  attain a deeper insight into that plan.—
We must  understand the connection between the
various parts of Creation, and, rising higher still, di-
rect our contemplations  to  the Author of all, who
has formed the whole and  subjected it to all  those
modifications extendi lg through long ages which
Geology has revealed, from the remotest epoch  up
to the period when Man was created and introduced
upon the surface of the globe with the animals and
plants which we now behold.
  Understand, then, that the study  and knowledge
of Nature  consist  in something   more than  ac-
quaintance with the isolated beings  which exist
upon  the surface of our globe.  We must under-
stand  the connections existing between these be-
ings,  and the relations which they sustain to th*
Creator of them all.
  But the question may be  asked, is it possible
for Man to acquire more than a superficial insight
into natural phenomena ?  This question has been
answered in many  different  ways.   Some  have
maintained that all we can expect to come at is an
artificial classification, agreeing in a greater or less
degree  with the natural phenomena; that a real
insight into all the  varied departments of Nature
by man is unattainable. But if we view the pro-
gress of natural science, and observe the investi-
gations made in every succeeding generation in the 
6
Prof. Agassiz's Lectures.
matter of isolated phenomena—if we bear in mind
how many things which appear isolated have been
combined into one and the same point of view, we
are furnished with a strong ground of hope that it
will be given unto Man to attain that insight into
Nature.
  There is another  reason why Man  may expect ■
fully to understand Nature.   We feel  in ourselves
that we are not mere matter.  We  have a soul.
We have  an intelligence.  We  have  feelings by
which we are in connection with each ot'.er. These
feelings—that intelligence—carry us  beyond the
limits of our globe.  We thus rise to the notion of
a God.  We have t'lat within ourselves which as-
sures us of a participation in the Divine Nature;
and it is a peculiar characteristic of Ma i to be able
to rise in  that way  above material Nature, and  to
understand intellectu lexistences.  The possibility
of obtaining au i..sight into Nature is thus strength-
ened by the analogy betweeu the Human and Di-
vine Natures. On that principle, Man  being made
in theimage of God, it is possible for his intelligence
to comprehend the doings of God in Nature.  Hence
by a constant intercourse with these works—by a
Natural Religion—by a constant study of these
works of Creation, we may come to understand the
views, the objects of the Creator  in doing these
works—in introducing these phenomena as realities
into existence.  We may, in one word, come to a
full understanding of Nature from the very reason
that we have an immortal soul.
   Again, our body is so similar to the bodies of ani-
mals.  The organization of our body discovers in-
timate relations with their physical condition.  We
pass from the lower type of animals so gradually
to the higher, until we find Man, with his superior
organization.   Thus  on  one hand we see that
owing to the intellectual nature of Man he has pe-
 culiar relations with the Author of all things, while
on the other band, from his physical nature he has
a root in the soil—a material foundation, and  hence
both the intellectual and the material world is laid
open to bis contemplation,  affording substantial
grounds for the belief that he is competent to at-
tain a full understanding of the works of creation
and the plan of  GoJ when bringing the world into
existence.
   That all this creation has not been  the result of
one creative act, we know from  geological ob-
servation.   This globe—the  animals which  exist
upon it now—have not been brought into existence
 at one moment.  We have learned from geological
observation that a long series of epochs have  suc-
ceeded each other, and that  during every  epoch
animals and plants, organic beings of various types,
were successively living and died away, to make
room for others, till the surface of the globe was oc-
 cupied by the animals and plants which now ex-
 ist with Man as their head.
   The most superficial knowledge of those pheno-
mena soon gave rise  to the notion  that the intro-
duction of Man has been the object of the creation
of this  globe, and the position which Man now oc-
cupies  upon the surface of this globe  is such that
this notion appears to us quite  natural.  I think it
may be shown  by actual demonstration, as Jar  as
physical phenomena can be demonstrated, that the
view of the Creator  in forming the  globe—in  al-
lowing it  to undergo these successive changes
which Geology has discovered, and in introducing
 gradually all these different types of animals which
have passed away, was, after all, to introduce Man
 upon the surface of our globe, and to bring him into
 connection with fhe  other organized beings and
 with the  soil in connection  with which he  does
now exist.
   There is one reason to believe that this is so. That
reason is this: We see from every point of view in
which we may regard the Animal Kingdom—and I
shall from this moment limit all my remarks to the
Animal Kingdom, in order not to trespass beyond
the  bounds  properly  set  to  this discourse—we
see that  Man  possesses  the  most complex and
most perfect  structure.  E ven his position is re-
markable and significant.  Man's erect position in
standing or walking shows that he is placed at the
head of creation.  All  the  lower animals  have a
horizontal position.  The  fishes  move horizontally.
Gradually as  we ascend in the scale of animated
beings we behold them raising their heads a little.
Snakes have no  feet, but they are able to elevate
the head;  and if we proceed farther we find suc-
cessive  typjs in which the position becomes an
oblique one, until the head is raised more  perpen-
dicularly.  But to Man alone is given the most im-
portant position—the vertical position, which allows
him to make use of his hand and  fingers and to raise
his eye directly toward the  heavens,  in this very
position—in this  material construction of his body,
we have an evidence of the superiority of man. But
in every respect, if we consider his structure, we
see that Man stands at the summit of animal being
—and that it is just so to regard Man as at the head
of Creation, will  be one object of these Lectures.
  Again, if we consider the construction of animals
upon the surface of our globe, we will find that the
lower types have been  first created—that they
belong to the most ancient rocks—that the deepest
rocks  contain none of the higher animals, and that
gradually some more perfect types were introduc-
ed till at last Man was created, and it may be shown
geologically, by actual investigation and withoutthe
slightest reference to  any  historical or sacred tra-
dition, that Man  has been created the last.
  Again, if it cannot be shown from this point of
view that  tli* introduction of man was actually the
object of the Creator, it may be at least shown
that Man was the last and most perfect work that
proceeded from  His almighty hand.  But that it
was actually the object of the Creator to introduce
Man at the head of the Animal Kingdom can, I hope,
be shown  by  combining the knowledge we have
acquired with regard to his physical structure, and
his relations with the different other classes of ani-
mals  and  with  the surface of the globe at large.
At no time do we find in geological  epochs a spe-
cies spread all overthe surface of our globe.  Every
type of animal—every variety of animal, occupies
in the geological epochs only a small portion of the
surface of the globe.  This fact holds  true in all
geological times.  Before the animals now living
were created—when  races entirely different from
them  existed, every  species was  circumscribed
within narrow limits,  and in no case  occupied the
whole surface of the globe.   No one of the species
of former epochs was superior to tbe whole type of
its time.  At no geological epoch do we find one
species standing preeminent above others.  But at
this present epoch, we find not only that Man stands
preeminent above all other  species, but that he oc-
cupies the whole surface of our globe; and in this
respect he appears to be of  a superior organization
and endowed with privileges which no  type ever
enjoyed before him.
   But I will not  dwell on those general questions
without some more precise  foundation.  1  shall at
once proceed to call your attention to the varied
types which exist in Nature, so as to have actual
facts upon which to reason.  I desire that the state-
ments with which I set out may be regarded as
the results of investigation and not as  matter of
mere speculative opinion.
   There is an astonishing variety of  animals upon
the surface of our globe.  This variety is such that 
Tlie  Animal  Kingdom.
 it is very difficult for the student who for the first
 time directs his attention to the subject, to perceive
. any order.  It is impossible at first to perceive the
 intimate affinities and the near relations which sub
  sist between all these varied formati > .s.
   I have here some diagrams giving outlines  of ft
 lew of these'..i-niatsons.  I .just name the  subjects
  before passing to their characteristics.   Here we
  have the  common star lis,i ofr.h>  M-ditn-rnnean
 Sea.   Here we have  one
 of  those  jellyfish  so com
 mon in temperate and wan.
 latitudes.   This is a specie! \
 common in the Atlantic—01.  "
 of the  species  whose  sub
 Stance in  more or less pho>
 phorescent.  Here is a cora
 o' the Hud Sea—a very com
 mon species.  Here  is a  cut
 tie-fish, ci■mmon on the west
 em shores of France.  Her. _
 a-e different species  of snakes, row
 Imli   and one from Central America.  H -raisaclam
 very common on  the south west shores of Africa—
 not the common species.   Here is the common lob-
 ster. Here is a worm, of that species having colon., I
 blood.  Here is a spider.  Here are  several skele-
 tons of vertebrated animals—an hyena—an ostrich
 —a crocodile—an enlarged skeleton of the bat.  I
 do not mention two of these animals, because al-
 though represented so perfectly, they are not now
 in existence.  They are  nowhere to be  found on
 the surface of the globe ;  but these representations
 have been made from preparations  most skillfully
 completed by attaching together isolated bonrs col-
 lected in the neighborhood"^!' Paris,  and  arranged
 into a complete animal  by the  wonderful attain-
 ments of  Cuvier  in  comparative  anatomy.  Thus
 these long extinct species of animals* are as well
 known to us  as if we had perfect  specimen* of
 them in our museums.
   Now, on looking at these diagrams the beginner
 in Natural History will be struck by the great appa
 rent dissimilarity between animals  whi. h yet be-
 long to the same family. Thns, how
 little  apparent  resemblance  be
 tween the star-fish and the coral!
 Then n:.'aiii, t\e cuttle-fish, the snai
 and the cl?m appear to have littli
 in common, and yet the affinity be
 tween them is  so close that the>
 appear  to the naturalist  as mem .
 bers of one and the  same  faruih
 And again, the  worm, the lobster
 the spider and the  butterfly  be-
 long to one  and  the same tribe.
 The  common earth-worm is  more  luiiuictr.eiy al-
 lied to the crab or the butterfly than to a snail or
 slug.  One might think that the leech and the slug
 were of a very  similar class.  Not  so.  Mere ex-
 ternal appearance alone  conveys an idea of iden-
 tity.  There is by no means any actual relation be-
 tween them.  The animals represented in the other
 diagrams constitute a fourth great division all ulti-
 mately allied.  The fish and the bat—the crocodile
 aDd the ostrich,  belong to one great type;  and the
 characters by which they may  be defined  are  cot
 artificial characters.   They  are not distinctions in-
 troduced by Man in order to facilitate his under-
 standing of those subjects and to  make bis classi-
 fication easy.  This intimate relation between them
 is a  natural one, derived  from their internal char-
 acter.
   It is very obvious that  here in this  star-fish,  the
star-like rays constitute the  prominent  charac-
teristic.   The rays  proceed  from  the  centre.—
The same character  is perceived in  the coral and
■"■		■3
f.v	*	. ,4
	ftV	- >'i
[■If	V	*i
V	i	■•.i
;	I	>
-:		i
:'. ■		■■■i
E?--		■ .4
 jelly-fish.  Here you perceive a similar radiated
 arrangement of the pa-ts.  The common cl nracter-
 istic of this  <rder ot a-imals is  this radiated ar-
 rangemi-iit from  the common centre, the  mouth.—
 The star-fish has at the lower surface an opening
 through which the food is introduced :  precisely
 the same arrangement is seen in the jelly fisb,which
 has a quadrangular mouth ; so, also, in the esse of
 the ool, p, surrounded by these fringes nrte.tRcu-
 lae.  Iu consequc nee oftl.ia peculiar
 ity these  nn'mals have  been de
 nomnated RcuUitcd :.?imals.
   ili ; next type contains anima'
 •*::";ii have very soft bodies an
 have  the power of contractin.
 themselves very much   If yon sl-
 a snail contract itse't.md  entirel
 disappear at the bottom of its shei:
 and atrain, if ^ou see it grow ou
 enlarging and expandio=r  itself f
 as to  have apparently  twice tl..
 eize of the shell itself; you will coi s  dt r tn.i u..s :s
 a faculty  which no other fyp?  cf animals  pos-
 sesses in such adegree.  No bird c n swell its body
 to twice or three times its r.aturfd size.  No quad-
 ruped can do that; no insect can do it. It is only
 in these animals that we see so  considerable  ex-
 pansion  and contraction.   Again, the movemeu'.s of
 this type are very sluggish.  No  one  of them can
 jump or run ; they can only creep upon the soil by
 successive contractions of  the  body.   A  few can
 «wim, but when swimming they are  moved in a
 peculiar mode by means . i'tliose appendages round
 the head.  Even th se have the power of contrac-
 tion in a degree which nooti'ertype of animal pos-
 sesses, and even here [pot.-itin. to the cuttle-fish]
 the locomotion is owing to this contraction.
   The whole body of this class  ia  covered by a
 dense mucosity, and  this  mucosity  makes these
 animals  very unpleasant to the touch;  and it  is a
 peculiarity of this aubstance to contain a ;,'rentdeal
 of mucus, which, to some, hug a very agrt-eable
 tf,ste, so that a great many of this ty pe are among
 the eatable animals.   Nevertheless, a great major-
 ity  of them please  only  in  consequence of the
 beauty and value of their covering.  For instance,
 shells, for many centuries, have been one of the
 subjects of greatest  'itr-.-ntion among  naturalists,
 and extensive collections of these coverings have
 been made everywhere,  while the actuals them-
 selves have been much  neglected ;  and we do -jot
 possess in our collections the soft parts of these an-
 imals, whi:h would enable  us to know them perhaps
 better than we do by their shells.  In fact, when
 we attempt to classify them from the shell, it is not
 more reasonable than if we should attempt to form
 a correct notion of the character of a people by look-
 ing at their coats! (Laughter.)
   The softness of this class of  animals is one of
 their main characteristics,  and  they are  all sym-
 metrica!.  They have a  right and left hand side,
 an anterior and a posterior extremity, an upper and
 a  lower  side.  From the  softnr«a of their bodies
 these animals have been called Mu!!i:«:a.
   [Here the learned  Professor  doi'io-.-strated the
 nervous system of this type by several diagrams on
 the board which he explained to his audience.]
   In the next type, we find together the lobster and
 the butterfly ! Nothing seem more dissimilar than
 the worm and lobster, and yet the structure is the
same.  The body of each ia formed  of rings, each
moving on the  anterior and  posterior ring.  The
rings may vary  in  hardness.  All do  not possess
rings so hard as those of the lobster.  Some lobsters
even have fi'lt. shells.  Some  animals of this class
have coverings as soft as the coverings of the  but-
terfly.  If we examine the  body of any insect, the 
8                               Prof. Agassiz's Lectures.
 spider, the butterfly or the grasshopper,  we find
 that it is divided into such a series  of rings, each
 movable on those anterior and posterior to it. Even
 in the worm—the leech—we have such rings, only
 in them they are very soft.  Thus we have already
 one character by which we can combine the worm
 with the crab or with the spider.   Between the spi-
 der and the insect with wings there is scarcely any
 difference but that constituted by the existence of
 wings. The wings are appendages  of no great im-
 portance when  considered with  reference to  the
 general organization of these animals-
   Bat the more striking and important difference
 between  these  two types is again to be seen in
 the nervous system: and it is a matter  of no little
 importance that the greatest difference between
 animals should be perceived in the nervous system
 —in the system which presides over the most im-
 portant functions of animals, and  by which their
 faculties are exhibited.  That again has the most
 striking character; and  always the  same arrange-
 ment of it, and the same relations to the other  or-
 gans are manifested whatever may be the exter-
 nal form of the animal.
   Now the nervous systems of the worm, spider and
 crab are so similar  that no difference will be per-
 ceived except by those who have  paid some atten-
 tion to these subjects.   [Here the learned gentle-
 man illustrated the nervous system of this type by
 diagrams  on the board.]  In the worm  it  will  be
 seen there is one nervous ganglion above the intes-
 tine, and all the jQKKK^"""=*~*^*i"^m..  '"* ii.»■  ■■
 others below- SS^rh'iM^VtlStSm^jS
 as many active gj*^^ ~s^Mfr»lg?SiwsM»g»j<Ssj
 centres of ner-
 vous influence as tuere are ruigs.  This affords an
 explanation of the well-known fact  that many  of
 these animals may be cut into pieces  and yet retain
 the power of regenerating the portions removed
 from the diffusion of the  nervous influence through
 these different parts of the animal.
  These details  may appear very  anatomical, and
 have little reference to the knowledge of animals in
 general, but I hope  it will he seen that without
such a foundation it is impossible to come to  an
understanding of the Animal Kingdom—without
which  we cannot arrive at a  knowledge  of our
own nature.  The  material, physical condition of
our own existence can by no means be understood
without a distinct and accurate idea of the struc-
ture of the inferior animals.  There is really no in-
 herent difficulty in these subjects.  Children might
 just as easily  be  instructed in this department of
 natural science as in  those subjects which usually
 occupy the first years of tuition.  (Applause.)
   The type of animals to which I have just directed
 your attention is called, from the peculiarity pointed
 out, the Articulata.              •
   The fourth type contains those animals which
 have this bony frame in their interior. Though only
 the hard portions  are represented in the diagrams,
 yet all have recognized the ostrich and the croco-
 dile.  These animals possess what is called a' back-
 bone'—a continuous column of bones from the head
 to the tail.  Under this column is a large cavity in
 which the organs of respiration and the intestines
 are contained.   On the anterior part of the body is
 the mouth—the opening of the intestinal tube; and
 the nose, the beginning  of the respiratory organs.
 Yet this is not the only cavity in the body of this
 order of animals.  We have in them the head, the
 cavity in which the brain is contained.  We  have
 beside all along the bony column a cavity in which
 is contained a substance called the spinal marrow,
 forming another nervous centre.  We have in fact
 two cavities of the body—one above and the other
 below.
  This type of  animals has received the name of
 the Verlebrala.
  So we have four great tribes of  animals charac-
 terized by peculiar external appearances as well
 as by internal differences, of which the nervous sys-
 tem presents as distinct characteristics as any other.
 Thus, the location  and arrangement of the nervous
 system in the rerlebrated animals present an essen-
 tial difference from the other types. In the Radiata
 and Mollusca and Articulata there is but one cavity
 in which the nervous system as well as the organs
 of respiration,  of circulation and  of digestion are
 contained;  while in the vertebrated  animals the
 two sets of organs, those which preside  over the
 functions of the will and those which  preside over
 the functions which maintain the body in its natural
 system, are distributed in two different cavities ,-
 the more important being in the upper and the oth-
 er in the lower.
  In the next Lecture I shall proceed to show that
notwithstanding this great variety of form in the
Animal Kingdom—notwithstanding the great differ-
ence in external appearances—these animals—all
of them in their types—are constructed on one and
the same identical  plan.  (Applause.)
LECTURE  II.
Infinite Wisdom displayed in the Animal Creation... .The Structure of Radiated Animals... .General Division of this
   Type....The Polyps....Their Mode of Subsistence and Digestion.... Mode of Reproduction....Have the PoItds «
   Nervous System?....Coral Reefs.                                                        «.iv/.Jt,o»
          CLASSIFICATION OF THE RADIATA.
 I..Polypi....................(Many tentacles.)
     1. Actinoida............(Ray.)
     2. Hydroida.............(Hydra-like.)
 II..AcALErHJE...............(Nettle skin.)
     1. Sxphuniphera......... (Siphon-bearing.)
     2. Discophcra...........(Disc-bearing.)
     3. Ctenophera...........(Having the tins of a crab.)
 III. .Echinodermatje.........(Skin with spines.)
     1. Asttro'idct.............(Star-like.)
     2. EchintiUz.............(Sea-eggs.)
     3. Holothurida...........(Worm-like.)

  Ladies and Gemlemen:  In beginning these
Lectures I endeavored to show that the student of
Natural History should aim at a higher object than
the mere knowledge of isolated phenomena—that
even the study of an accurate classification is not
the highest point to which our effort can arrive
There is a more elevated view of the study of Na-
ture than that, which we should always  keep in
sight when we enter on such a field of investiga-
tion.  It is to consider Nature as a development of
the thoughts of the Creator.  Regarded  in that
aspect every object at once assumes a greater im-
portance, and becomes invested with new and su-
perior value in our eyes.
• ?hfr?,was aDOther Po^t which I touched, but on
it I shall not now dwell, as I shall repeatedly have
occasion to show that it is the true view in which
we should  prosecute these studies—and that was, 
The  Animal
Kingdom.
9
that there is a plan, a general plan, in the works
of Creation.  We will be able to show that even
isolated daises are  made according to one precise
plan; yea, that we  must refer at once the creation
of  these  things to  the understanding of a higher
Power, a greater Wisdom, than  man's power  or
man's wisdom.
  After these  preliminary  remarks, I proceed  to
show that the Animal Kingdom is constructed ac-
cording to four different modifications of the ar-
rangement of the parts.
  What  naturalists  intend  when  they  speak of
what they call " types " of the Animal Kingdom
may be easily understood by comparison.   We all
know that architects construct our dwellings  ac-
cording to plans conceived by them before the erec-
tion of the edifice; and if we  take a general view
of the works of domestic architecture we shall see
that they all agree in one respect. They are spaces
circumscribed by walls,  covered by a roof, and are
designed  to afford shelter, comfort, and even all the
luxuries  of life.  All these  structures, from the
humblest hut to the proudest palace, agree  in this
general object, and we  may  say that they are all
constructed according to one plan, though it may
be subjected to endless variety of modification.
  Again,  those who have studied  and  practiced
music know very well that they can, from a funda-
mental harmony, produce a great many variations,
and yetr  among  these  variations they will very
readily recognize the principal tune.  Well, in Na-
ture we will readily discover  one fundamental har-
mony throughout the works of Creation, and we
will soon  perceive that the  variations of the differ-
ent types can all be reduced to that general princi-
ple.  Nay, we can go farther and recognize in these
four types a fundamental idea which is common to
all.  The fundamental tune  in the Animal Kingdom
is life, while the endless varieties are the  thoughts
of the Creator diversified in an infinite degree, and
all in such a way as altogether  transcends the in-
telligence or  even the  fancy of Man.   Thus,  in
whatever way we regard this subject, our contem-
plations must always at last fix on the great Archi-
tect of the Universe.
  These four plans  are,  as  I  mentioned;  first, the
 Vcrtebralo, to which Man belongs, and the  higher
animals as we call them, the mammalia, birds, rep-
tiles and  fishes.  They  all  agree in one respect—
that they have an internal frame of bones surround-
ed by flesh, and that under this  covering of hard
and soft parts theie are cavities containing the
viscera—the different organs by which we digest
our food, and breathe, and by which the  blood  is
circulated ;  and another cavity above that contain-
ing the  organs of the higher functions of animal
life, the brain and  spinal marrow,  the organs  of
sense, the nerves.  This type has an arrangement
of parts which may be expressed by a very simple
formula;  and as chemists have adopted formula; to
express  the composition of inorganic bodies, we
may adopt formula? to express the  general struc-
ture of organized beings.  A  figure, then, like the
numeral 8 would express the  general arrangement
of parts in till vertebrated animals.  The centre of
the two bodies being the body of the vertebral col-
umn ; the upper arch, or cavity, representing the
cavity containing the brain, and forming the upper
region of the animal, and this lower cavity contain-
ing  the viscera—all surrounded by fleshy  parts
from which some appendages in the higher animals
proceed to form the  limbs.  I  shall have  occasion
to show how the arms and legs all conform to the
different arrangements of the  Verlcbrata.  We can
trace these  modifications from the lower type  of
fishes, where the arms continue attached in contin-
uous form—or snakes, where there are no  external
legs, nevertheless there are some such organs of
locomotion connected with the  walls of the body.
All these analogies may be traced and be actually
shown by direct demonstration.
  The next type  is that of the Articulata: then
there is the Alollnsca, the third ; and the Radiata,
the fourth type. All these three types agree in one
respect, that their organs are contained in one and
the same cavity.  There is but one cavity.  But
the nervous system, as I showed, differs in its gen-
eral arrangement, and all differ in another essential
point—in  the mode in which  they are formed.—
When speaking of the formation of animals within
the egg, I shall have occasion to show how funda-
mental are these differences.   They are such that
the germ of an articulated animal is formed just re-
versely to that of the Mollusca.   These differences
in the formation of the animal have been traced in
so many animals from the egg up to the period of
full growth, that there can be no doubt on the sub-
ject, and there can be no doubt that the peculiarity
in the location of the nervous centre in the lower
portion of the body of the Articulata has reference
to the mode of formation of the germ and develop-
ment of  the raw individual.
  These facts may be very readily observed in the
eggs of the crab and  the spider.  It is more difficult
to investigate this in the eggs  of insects, because
they are not so transparent.  In them the delicate
process of the formation of  the new individual is
not easily traced.  But in the crab it is very easy
to observe it. I  need hardly say that this is one
of the most interesting and  wonderful things in
the study of the Animal Kingdom.
  In the first type, all the parts [branch as it were
in all directions and  form  a radiated  animal; and
in these different rayswe see ^.-cs of the alimentary
canal, so there is no anterior and posterior reu- ion, ow-
ing to the general adaptation of the parts to the gen-
eral arrangement. Perhaps the differences  which
are notorious between the form of types may not be
easily comprehended now, but I hope when enter-
ing into more details with reference to the struc-
ture of the various types to  make this part of the
subject better understood.
  My object in this recapitulation was to show that
this division of the  Animal Kingdom was really
based on this intimate structure—on the very foun-
dation of the  plan according to which they have
been  constructed; and that this division has not
been adopted merely for external differences per-
ceived between  the variousjtypes of the Animal
Kingdom.
  I shall now proceed to demonstrate the structure
of the radiated animals.
  My object in beginning with the lowest type of
animals  is to show how wonderfully organized are
those beings even which occupy the  most inferior
condition of existence.  Their organization is  in-
deed so simple that for a long time they were con-
sidered as wanting in internal structure.  But more
minute investigation has shown that even the low-
est cf the radiated  animals have a structure infi-
nitely more complicated than was at first supposed.
They all agree in one respect—they have all a radi-
ated form.
  I have here before me oneof those animals which
show this  radiated appearance  most distinctly. It
is a star fish,  of the  common species, found living
on the American  shores of the Atlantic.  All radi-
ated animals have not this radiated appearance so
distinctly marked ; but in most  of them it can be
readily perceived when they  are subjected to suf-
ficient observation.  In some it  is traced with diffi-
culty, owing to the very minute size of the animal
There are a great many  of the radiated  animals
whose entire  'ergth is scarcely  a line or even less 
10
Prof. Agassiz's Lectures.
than that; but there  are others again, such as the
starfish, whose tize is so considerable a9 to amount
to one or two ffct diameter.
  The whole type of radiated animals may be di-
vided into three classes: the polyps, containing the
coral; the jelly-fishes, and the star-fishes.
  In their  extern \\  appearance these classes do
not differ very much.   [Here the lecturer directed
the attention of his auditors to several illus'ratio.is
of the various classes of radiated animals.]  But
in their internal structure they differ widely.   All
polyps have one single cavity in which all  the or-
gans are contained;  and all these organs consist
only of a large stomach and some groups of eggs
arranged around the stomach.  By means of their
tentacles they seize  on their prey.   In the centre
is the  mouth.  Here is the general substance of
the body, formed ot fleshy material, its walls being
vertical lines.  This animal is very soft in its sub-
stance.  It is fleshy, and when touched contracts
suddenly.   It closes its tentacles entirely when
touched ; its mouth is also contracted  in that case,
and assumes a spherical  form, showing  no trace
whatever  of  the  beautiful  external appearance
which you see represented  in the drawing.  The
vertical  folds  which are here scarcely perceived
become marked and distinct.
  Jf such ai animal be cut vertically,  you will see
that it contains one large cavity, with a wide open-
ing below.  Through that opening j on
enter  another  cavity.  The  wallti of
these cavities are fids which  are tin
partitions  runnimr to  the  periphery
S>me of these fo1 is will not run to the
stomach, and form only subdivisions ol
the principal p.r i ious. Between the
two cavities there is. as I have said
a wide opining.   This structure  io
convnon to all p-.ilyps   T'.rf organtzi-
tion of this class.is now  pretty welt
known, though, it has not been lo.itr sMidtu<i win mi-
nute atttntion.   This augmented knowledge of po-
lyps is owinjr '. i ri,e efforts of the naturalists of the
Exploring Expedition of this country under Captain
Wilkes. (App'nu'e.) Va'aableonti ibutionF t> this
department of NVur.il History hnve also be a made
by Mr. Dana.  His work must alwayt. be a standard
authority.   (A, plause.)
  On entering into some  more minute details of
these animals, it will be seen that this organization
is very interesting.   We e;tu here trace the  ani-
mal Junctions  in their lowest  condition.  How do
these animals live?  The food is seized by these
tentacles.  The whole surface of the  te-./i-acles is
covered  with  microscopic  vibratory  ciiU—little,
soft, projecting hairs, so minute as  to  be discerni-
ble only under  a microscope of very considerable
power.  Unlets you apply  two hundred and  fifty
diameters—which  is a very considerable power—
you can scarcely perceive  these little cilia.  But
under such a magnifying power you see the entire
surface of these tentacles covered, as it were, with
hairs, and these  hairs  are in  constant,  incessant
motion  in  different directions.   A  continuous
current of  water is  thus  maintained  by these
minute  appendages.   Here again, in the open-
ing, these vibratory cilia are constantly in motion ;
and in the internal cavity there are also seen vibra-
tory cilia moving constantly.   They  are not under
the control of the nerves—not under the  control of
the will. They move incessantly.  From the mo-
ment the  animal escapes from tbe esg, and even
when withit; the egg. they are  in motion.  Daring
the whole period of life these cilia do not cease to
move.  They act by  day and ni^ht.  Daring the
rest of the animal, as well as during the more ac-
tive periods  of its existence, these unwearied or-
gans are at work.
  Now, it is owing to the action of these cilia that
minute portions  of organic matter are introduced
into the animal's  mouth.  A considerable space of
severalincl.es in oiameter is swept by these ten-
taculse.  All  the  little  particles—imperceptible  ti
rue eye—of animal matter, of decomposed vegeta-
ble matter, shells, and soon,  are  thus brought into
the mouth, and thus food is supplied to the animal
incapable of moving or running after other prey—
This is the mode  in  which Nature has provided for
t!i ■ sustenance of these animals.
  But  beside this mode of alimentation,  these  ani>
mals can contract their tentacles and seize upon
large prey. Polyps of a few inches in diameter will
seize a fish, surrounding it with their tentacles and
introducing it into their mouth, after which it is di-
gested very rapidly. Now this mode of alimenta-
tion is  performed  in a very  interesting  way.  The
tentacle of such  a  polyp  is a very complicated
structure.  I  had an opportunity lately to study
its  microscopic  structure,  and 1 have foundthat
each tentacle, examined under considerable micros-
copic power,  is a tube whose walls are formed of
longitudinal muscular fibres—fibres similar in struc-
ture to the muscles of the higher animals.  By their
contraction these fibre3 can shorten tbe tentacle in
all directions; or if excited only on  one side they
will curve it on that side.  Then, again, there are
other  circular fibres around the whole tube, and
these  pull the tentacle in succession, so as to elon-
gate it to them in four times its usual length.  Thus
the animal is  enabled to seize upon larger prey.
  Such ia the manner in which  the food is intro-
duced  into the  internal cavity.   This cavity is a
simple sac, and even a sac which is open at both
ends.  But then the ends may be contracted and
shut at the animal's pleasure.   When the whole
animal is contracted, both these openings  of the
stomach are  thut, and  when the animal has filled
its  stomach  viti. food the lower openih;.; of the
stomach is closed  But as soon as the food i- within
tha1: cavity it  comes in contact with some secretion,
probably similar to the bile or the salivary fluid of
higher animals.  At all events, it is subjected  to
the influence of some agent the character of which
has not yet bcu  ascertained, but should be  ascer-
tained, as the u.niui:i.l is very common on the shores
of this Continent.  Digestion is rapid in these ani-
mals.  Kven  shells  are speedily assimilated, the
hard parts  being rejected  by the mouth, and the
juices produced under the influence of the walls of
tiit;  stomach  are diffused into  the lower  cavity.
fiie food is  introduced into  the stomach  with a
certain quantity  of  water, so that tie food  is
from the beginning mixed with a quantity of wa-
ter, but the moment the food  has been digested in
the stomach,  it passes into this lower cavity, and is
there mixed with a  greater  quantity of water.—
Now this digested food begins to move in the whole
cavity, and to move  between all these  partitions ;
and the motion is  produced in  a way similar to that
of the  tentacles.   These partitions have the  whole
of their surface covered with vibratory cilia, so that
the water containing the alimentary substance  is
constantly  moving between them.  The refuse  of
the water escapes through the tentacles. We have
here the digestive function, as it were, combined or
mixed  with a kind of circulation.  There is indeed
no blood in these animals—no vessels—no respira-
tion proper. There is only one large cavity divided
into two sacs, the upper one digesting the food, and
then we have this digested food mixed with water,
and  this fluid again diffused throughout a  great
many smaller cavities in  contact with the walls  of
the animal.  These walls absorb the fluid  like a 
The  Animal  Kingdom.
11
sponge, and the alimentary portions remain within
the body of the animal, while the superfluous wa-
ter escapes through the tentacles.  Of course the
contact of the water produces a kind of respiration.
There is undoubtedly a change of substance con-
stantly produced between the external water and
the internal fluid.
  The eggs, which  are very  numerous  in these
animals, are hung in  bunches  as numerous as the
partitions.   There are polyps in which  there are
twenty and in some a greater  number of bunches
of eggs  hung around the lower opening of the
stomach or on the internal wall of these partitions.
When the eggs are ripe they escape either through
the stomach and mouth, or between the partitions
through the tentacles.   In the course of this Sum-
mer 1 have witnessed repeatedly this operation in
one  of those polyps which  are  common on these
shores.  They may  very often  be found on the
piles of tbe  wharves all along the shores of the At-
lantic.  In some of them I have witnessed the pro-
cess from the earliest stage.  When the young ani-
mals escape from the egg,  they have the  same
shape as the old one, but with  this difference, that
they have only five  or ten  tentacles arranged in
such a way (making a diagram on the board); af-
terward they have five  additional tentacles, and so
go on increasing till these appendages become al-
most innumerable. I have found that these tenta-
cles are uniformly multiples  of five.
   The mouth appears to be circular, but when care-
fully examined it is found to have an elongated ap-
pearance.   In fact, the mouth is rather oblong, and
in the young animal  that form is quite apparent.—
You  will perceive that  in the youug animal one of
the tentacles is just parallel with the straight line of
the mouth, and the four others  are arranged in two
pairs literally. This point is important, as I shall
show that there we have the first indication of bilat-
eral symmetry with the anterior region well defined.
   No nerves have been observed in these animals.
Nevertheless,  we cannot doubt that they feel.—
Light acts upon them.  They contract under strong
light. They  also c jntract under the influence of
darkness.  In mild light they  expand completely.
Borne, indeed, can expand in the  strongest light.—
This shows certainly that the sensation of light is
perceptible to them.
   In some  of  the polyps I have observed dark
specks, corresponding in number with the tentacles.
We may he allowed to conjecture that  the specks
are eyes, and if so there can  be no doubt that there
are nerves.   Ia fact, in the star-fish the nerves have
been seen.   They have  been traced up to  these
colored specks.
   This is about all that can be said of the structure
of tbe polyps.  Their external form is very various.
I will mention some  of them in order to show the
variety of  types among them.  All those which
have numerous tentacles, and the internal cavities
with bunches of eggs hanging from the walls of the
lower cavity, have been named sea-anemones.—
Borne are entirely soft. Others have, inside, a hard
framework  formed of limestone—of carbonate of
lime—and in this  framework one can see the  same
radiated appearance which we can see in the  type,
which is entirely soft.
  You see  in this specimen an illustration  of the
remarks just now made. It is not correct to regard
these corals as the shells in  which  these animals
cover themselves.  The hard parts are found with-
in the animal and form a portion  of their internal
structure.  There  are a great many of them in
which the hard parts are deposited within like net-
work. [Here the lecturer pointed to specimens in
illustration.]
  The polyps do  not  all multiply only by eggs,
though all will lay eggs and multiply in that mimiftr.
Some produce buds on their surface
and these buds will grow and re
main attached to the main body.and
 in that manner the buds will be
come branched.  Perhaps a little
polyp attached to a rock assumes j
such a form.  After a certain time I
we see a small bud, which enlarges I
in the same form, nndgrowsandpushesour.ua tcata-
                  cles in the same manner as the
                  first individual. Thus from this
                  branch a new individual will be
                  'brmed and remain  connected
                  ■with the parent stem.  In that
                  manner we have compound an-
                  imals, and that is the case with
                  most of corals where a great
may individuals are united  in one  and the same
stem, while others remain single.
  The importance of these  animals is very great,
from the well-known coral reefs. Beside, these an-
imals act in a very extensive manner in  modifying
the shades of the  ocean's depth.  They contribute
in the formation of islands and in enlarging conti-
nents, by increasing the amount of hard substances
deposited on the surface of  the earth.  We know
from  geological researches  that  whole  mountain
ranges  have  been formed  by the agency of this
 minute animal. But this is not the place in which
to speak of this geological phenomenon.  I allude
to it at present only for the purpose of showing the
importance of the  functions performed by this little
 animal in Nature.  There are  some  polyps which
 produce eggs and buds, but it is only some of the lat-
 ter which can  in their turn produce epgs.  A great
many of the animals classified in the Infusoria are
only eggs of polyps and other lower animals swim-
 ming freely by the agency  of their vibratory cilia,
 which cover  the  surface of the egg-shell.   The
 sieds of plants are in the same way covered by
 ciiia, and, moving  freely in the  water, are also often
classed  with  the infusoria.   There are  plants
called Confrrva, divided  by partitions in the man-
ner  which  I  have described, and  the  seeds are
covered  with  vibratory   cilia, moving  so freely
in the water that they cannot  be  distinguished
from  toe lower animals.   They are so minute that
 an examination of their internal structure is a mat-
ter of very  great difficulty.  If we could only  as-
certain whether they have  a stomach,  their posi-
tion among organized beings would be very easily
fixed.  But as they are so minute that the highest
microscopic power discloses only these vibratory
cilia, and as there are animals which have been
discovered  to  possess a  stomach very closely re-
sembling them in  external appearance, it is very
difficult indeed to  determine whether  they  belong
to the animal or vegetable kingdoms.
  Locomotion, as such, is not  a distinctive charac-
ter of animal  life.  It  is only the wilful  motion
under  the action of nerves which is characteristic
of the Animal Kingdom.  But vibratory motion, pro-
duced by these minute hairs covering the surface of
minute animals and plants, is common to organ-
ized beings in general, and is  found as well in the
vegetable as in the animal kingdom.
  Polyps are divided into two great families: the Ac-
tinia, in which the eggs are arranged in bunchesin-
terually, and Hydroida. which  have tentacles in the
same manner as the others,  but in which the eggs
hang in  bunches externally from the  lower end of
the upper cavity, in graceful forms and sometimes
beautifully colored.
  The hour is now so far advanced that I cannot en-
ter into the consideration of other classes of radiated
animals. I shall take them up  in my next Lecture. 
12
Prof.  Agassiz's Lectures.
LECTURE  III.
                       .,  oi        r iv.  -d«i™   rpv,e r;r»nd Distinctions between Animals and Plants....
Additional Facts Relative to the Structure of the'Polyps... .The J "^   fho!pbore,celll;e of the Ocean in part
   Organization of the Egg....The Acalephae---Structure ot the Jeu£-iH»n....i:uuj>i «_r ^___^  f ^._ anania/
    Produced by the Medusae---Difference be
    'iscoveries of Sars, Krohn and Chamesso.
   Structure of this Species....Mode of Loco
   in this Department of the Work of Creation.
I Difference'beiweenThe-poTyp. and Medusa,... ^.^^^^^^ '"
»nH PhampMo   The Echinodermata___Interesting Held ol investigation upon....
      o? Locomotion. ..Digestive and Circulatory Apparatus....Evidence ofDesign
  Ladies and Gentlemen :  The last Lecture was
occupied in tracing the characteristic features of
the polyps—the lowest of the radiated animals.  I
showed how simple, and nevertheless how beauti-
fal and well adapted the structure of these animals
is.  We find  in them only one organ, and  yet we
find almost all the functions of animal life.  That
one organ is  the stomach—au  ample cavity with
two openings,  a mouth and a hole at the bottom of
the sac emptying  into the general cavity of the
body; thus the food when  digested is mixed  with
water which constantly  fills the general cavity of
the body. This mixture of sea-water is constantly
set in motion by capillary cilia  or hair-like append
ages covering the whole surface  of the internal
cavity as well as the internal cavity  of the tenta-
cles, and by the partitions which run from the ex-
ternal wall of the animal toward the centre of that
cavity  thus filled with water, which is then kept in
motion  in  different currents, some ascending,
others descending, so that there is constantly kept
up a circulation of tbe digested food.  The walls of
the animal are permeable to this liquid—that portion
which is nutritive  remains in the walls of the ani-
mal, while the water which has been the vehicle for
this food is pushed out by the  contraction of the
animal.
  There are two exits for the food, either through
the mouth again, or by the small  openings in the
tentacles. The water which fills the  general  cavi-
ty enters also through the tentacles and  the mouth
—alternately through one  or  the  other.  But as
there are muscular fibres similar to the flesh of
higher animals which can be elongated by gradual
contraction or expansion, this cavity can be alter-
nately  shut, so that by the contraction of the mouth
the introduction of water may  be allowed  or pre-
vented.  The contents of the stomach may be kept
within the cavity by the contraction  of the lower
opening of the  intestinal cavity,  and  again the
tentacles can contract at their  end and so prevent
the water from escaping;  and while the digested
food is moving with the water  within the  cavity,
with the tentacles thus contracted, nothing escapes
.—but after the nutritive portion  of the food has
been absorbed by the walls of the animal, then the
water is allowed to  escape through its mouth, as
well as the other opening.  An agency or influence
is undoubtedly exerted upon tbe surface of the ani-
mal by the surrounding water which may be  com-
pared to the respiration of animals that live in the
water.   There is something similar to bronchial res-
piration in some] of the lower  animals,  especially
the Mollusca, where  the action of the water acts
on the fluids in the animals and produces upon  them
a change which enables the fluid to become a por-
tion of the  living  creature.   These  changes are
very complicated and not all  fully understood.—
There is much room for investigation with reference
to the changes which the food  undergoes in  order
that it may become a portion of the living animal.
What  is more wonderful than what we see every
day—a cow grazing and  turning  the  grass into
brain, muscles, bone ! That is constantly going on;
and different  animals produce  the  same  changes
upon common food, with different organs, but  in all
the same result. Thus the same food is transformed
in one case  into the body of the  hare; in another
into that of the deer; and in another into the body
of the elephant. With the same food these ani-
mals  not  only reproduce, but  create, as  it were,
their bodies, under the influence of the  primitive
material principle which is the cause of their exis-

  Another system of organs existing in the polypi
are the ovaries, hanging in bunches either in the in-
ternal cavity or outside on the tentacles.  These
two forms have been the foundation of  the  two
great divisions of the  polypi, namely, the Acttnoi-
dm, tbe name  derived  from the Greek word for
" ray," and the Hydroida,beca.xise these animals re-
semble  that one which has been called the hydra
—a  name reminding  you  of a  fearful animal.
Thus  these harmless, minute, almost microscopic
animals have received that formidable name.
  You see here (pointing to a diagram) eggs forming
on the outer side.  Some are not isolated as in this
case.  In many instances the eggs hang in bunches
—as you have them here, for  instance, in another
diagram.
  I then alluded to  other differences in polypi,
where some were  isolated individuals and others
combined ; the latter budding on one and the same
stem, thus forming three large groups of individuals
united by their base.  It is a peculiarity of polypi
to be fixed on the soil. There are no free swimming
animals among them.  Some are attached to other
bodies at the bottom of  the  sea.  Some  are fixed
at willor move at will from their location; but there
are none among them who swim freely in the wa-
ter.  In this  respect  many of them have  some
likeness to plants, and were indeed long mistaken
for  plants.  Even so late as the middle of the
eighteenth century,  naturalists  quarreled about
the vegetable or  animal nature of polyps.  But
it is now fully understood that they belong to the
Animal  Kingdom;  while, on the other hand, many
organizations which belong truly to the vegeta-
ble  kingdom have been introduced among the poly-
pi, and  must of course be rejected from that class
and be again classed among the plants.   There is,
indeed,  some difficulty in distinguishing  some of
the lower types of  plants and animals.   I have al-
ready alluded to  one  grand distinction  between
them. Tbe existence of a stomach is a chief char-
acteristic of, an animal, and no being should be intro-
duced into the Animal Kingdom in which a stom-
ach does not exist.  But as there is great difficulty
in ascertaining in some of the lower animals wheth-
er there is an alimentary cavity or not,  we must
take other characteristics by  which they can be
distinguished ; and we have now a very  remarka-
ble test by which we can determine  whether an or-
ganized being is a plant or an animal.  In the mode
of respiration we  may, by chemical analysis, dis-
cover whether an  animal or a plant is before us.
All animals  in respiration assimilate oxygen and
reject carbon, while plants assimilate carbon and
reject oxygen.  There is thus a constant antagon-
ism between the animal and vegetable kingdoms.
All animals  would die were it not for the breathing
of plants, and all plants would perish did animals
cease to respire.  The antagonism is such that the
whole amount of animals living, now consume pre- 
The  Animal  Kingdom.
13
cisely the amount of oxygen which  plants expel
during the night, and by this antagonism between
the  animal and vegetable ^kingdoms, the constant
and unvarying equilibrium of the atmospheric air
is maintained.   Now  when we want to know
whether we have before us a microscopic  animal
or amicroscopic plant.all we have to do is to examine
the nature of the gas absorbed or expelled in res
piration.
   Another test may be as certain.  That test con-
sists in the examination of the egg. The eggs of all
animals,without any exception, from the polypi up to
the mammalia, are identical. There is not the slight-
est  difference in their structure—in the internal
and minute structure of the eggs of  all classes of
the Animal Kingdom.  There are differences in size
but not in  structure.  The egg of
a fish is full of granules.  In the
class represented in this diagram
they are about the size of a pin's
head. In some fishes the granules
are still more minute. Inside of
this yolk  there  is  another  little
vesicle which is called the ger-
minative vesicle;  and in  that  we  have  either
another or several cells of a smaller size which
are called  germinative dots.  These cells in a cell,
containing granules of yolk, constitute a character-
istic which you will find  without exception  in all
eggs.  In  a bird's  egg, the shell and white of egg
are accessories, but not necessary to the actual for-
mation of the chick, which is formed from the yolk,
and not from the white or  any other portion of the
                      egg.  Now this yolk, or vi-
                      tellus as it is called, fills the
                      essential portion of the egg,
                      and within that is  another
                      vesicle  filled with a trans-
                      parent liquid in which sev-
                      eral other similar vesicles
                       swim.  This  constant and
                      uniform structure of the egg
affords a test whereby we can ascertain whether
the organized being before us  is an animal.  The
eggs may  be as easily perceived in the lower ani-
mals as in  the highest, as they are so transparent
that they are readily examined under the micros-
cope.   Now these  eggs differ entirely  from the
seeds of plants.   Even in the conferva these seeds
are filled only with uniform granules  and have no
intricate minor cells;  and  now, when these eggs
become movable by having the whole surface cov-
ered with vibratory cilia, we have only to put them
under the microscope in order to decide whether
we have before us the  seed of a plant or the mov-
 able egg of an animal.  (Applause.)
   I will now proceed to demonstrate  another class
of  these  animals—the  Acalepha,  or  " nettle-
skinned."
  The name of this class is derived from peculiar-
ities in these animals  which I shall  immediately
explain. You have examples of Medusa in these
diagrams.  They have many relations to the polypi,
but there is one general characteristic which will
Strike you when it is mentioned.   The medusaa are
all free—independent  of the soil.  They have no
point of attachment.  They cannot fix themselves
upon the soil.  They  have  no  means by which
they can become attached ; and all have the mouth
downward, while all polyps have the mouth up-
ward.   In  the very position of the animal  in  the
Burrounding element we have one great difference,
which is as constant as the  moat intricate peculiar-
ity of their  structure.   There are a few moving ani-
mals in which the difference of internal structure
between them and the polypi is  by no means very
apparent; they have not one organ more  than we
have seen among the polypi, only a little complica-
tion of the same organs.
  In the jelly-fish  we have abroad  disc, and in
that a wide  cavity, with a mouth in the centre,
from which several, sometimes numerous, append-
ages hang down. This is the simplest structure of
the medusts.   There the mass of the animal is con-
stantly gelatinous.   The bodies of this class are
exceedingly soft, so much so that  when taken out
of the water they  almost  wholly decompose and
disappear. They contain so very little substance
that a cart-load of  them would not,  if dried by
evaporation, leave an ounce of hard substance—of
dried membrane.  A single leaf of paper would
contain as much solid matter as a full cart-load of
these animals when dried.  They are so liquid that
they are transparent—so much so that they are fre-
quently not seen in the water,  and would not be
perceived at  all if it were  not for  their beautiful
colors.  They have, indeed, the most beautiful, del-
icate colors of all the lower animals. Again,  a
great number of them are phosphorescent. In the
night they appear like brilliant lights, and to some
of them is owing the phosphorescence of the sea;—
not to them solely,  for the phosphorescence of the
sea is produced by a great  number  of  animals.
Very numerous and  different species  of animals
produce that  peculiar, beautiful  light that illumes
the  sea during the night. Some of these animals
belong to the articulated types, others to the medu-
sa? ; some are polyps; and  perhaps the light is in
part owing to physical causes—the decomposition
of animal and vegetable matter; and perhaps also
to electricity.  There is some doubt as to the rela-
tive agency of these  various causes in producing
the  phosphorescence of the  ocean.
  The great  difference  between the medusae  and
the polyps is that the alimentary cavity is no longer
a simple sac with simple openings. The cavity has
branches  penetrating into the substance of the
animal, so that  we have no longer a simple sac
opening into the general cavity, but a sac  with
ramifications.   You perceive in this diagram some
of these ramifications. They are so delicate that
they can hardly be shown  without exaggerating
the colors.  Let me illustrate this peculiarity of the
structure of this class of the i
radiated animals.   Let that ]
(diagram) represent the cen
tral opening, sometimes angu
lar,  sometimes pentangular •.
from that,  light appendages
extend toward the periphery,
but soon divide like blood-ves- I
sels; and these sacs will sometimes divide with nu-
merous tubes, and form as many canals as the most
complicated blood-vessel in its divisions.   In that
way the food, after it has been digested, is carried
into  the parts.  It is no  longer in contact with one
surface  only.   It is now carried into the different
parts of the animal. It is as  if the stomach were at
the same time a heart, forcing the digested food into
the cavities, as the  heart propels the blood into all
portions of the body. But here this food, after it has
arrived  at the periphery, escapes.  There are as
many outlets  as there are tubes.  And  again, there
are from the periphery numerous  minute append-
ages, like tentacles, with an  opening  at the end,
which absorb, pump the water and introduce it into
a canal which runs all round the animal.  So we
have no longer the  food introduced into a cavity
containing water, but we have the alimentary canal
branching in all directions; and in the extremity of
these branches we have small tubes absorbing wa-
ter and mixing it with the  food.   These tentacles
form beautiful  appendages  in  a great many of
these animals.  They vary  very much in different
 
Prof.   Agassiz's Lectures.
14

animals.  In some the appendages are longer than
the body of the animal itselt.  I., others they are
quite short.   In some they meet regularly and orm
triangles   In some they are few in number bu; of
large size.  But in all they are hollo *r, h .»d they ab-
sorb water, ami also admit the digested ; jod, which
is circulated  through these  tubes and induced
into this circular canal,  i'he motion ot the fluids, is
not iu a uniform direction.  Sometimes it is  one
way, sometimes another. It is an irregular circula-
tion, which changes its direction.  In some of the
higher animals, the heart causes the blood to rush in
one direction, and, after it returns, propels it in ano-
ther direction, so that in one and  the  same animal
we have the heart  acting in  different directions,
and we have that sin^lar phenomena in  some ot
tbe medusaj.   In this respect we have a complies,
tion  which exists in very few of the  polypi. It is
round these  appendages that  the  ovaries usually
hang in large bunches.  These colored bunches are
bundles of eggs  hanging  outside the  tentacles
which surround the mouth.
   In some  of these  animals, colored  specks have
been seen between the  tentacles, usually red, and
they have been conjectured, not  without probabili-
ty, to be eyes.
   This  is about all that is known of the structure
of these animals.  There are several varieties of
them.  Some have large gelatinous discs;  they are
the common  jelly-fish.  Others have a large vesi-
cle above the tentacles and compact portion of the
animal, which allocs thetn  t.> swim on the surface
of the water. Others have a great many of these
vesicles.  Others again have vertical series of sin-
gular appendages acting like oars, by which they
move very rapidly in the  water  The locomotion
of the first class, those  having a disc, is.owing to
the expansion and c infraction of the disc.   The lo-
comotion of the sreoud class is owing to the motion
of the tentacles and  the contraction of the air ves-
sels ; while that of the third class is owing to those
series o( vertical appendages.
   In their mode of growth they  present most ex-
traordiuary.phenomena.  Not all of them have been
studied, but those which have been exa ained pre-
sent these phenomena.   The Swedish naturalist,
Sars, has discovered that  the eggs of the common
medusa of the Baltic Sea we.e  movable.  This
might appear almost incredible,  had  not repeated
subsequent observation  established  tbe   fact.   I
shah endeavor to illustrate the formation of the
egg.  Iu an egg of this form  the  enlarged upper
portion  begins  to grow  with  four appendages—
these   appendages  forming  a star-like  animal.
It graduali>  changes its form, and assumes the ap-
pearance of  the polyp, for which it has sometimes
been mistaken. The number of tentacles increases ;
as many as sixteen and twenty tentacles  are now
seen, with much change in the general form.  Then
a considerable change commences.  This animal,
with all its tentacles at the upper end, begins to
contract, transversely, just as if it  were pressed in
different places ;  and these contractions increase,
so as to form, very soon, several stages one above
the  other,  like  a  series of independent cups,
only from the contraction of the primitive trunk of
this polyp-like animal.  This internal column, re-
sembling tbe back bone, which keeps them togeth-
 er, still continues to contract so  far that the cups
soon divide into as many individuals, and become
free, movable from that time, and turn in  opposite
directions.  Before  they  separate, the margin is
 fringed—divided in such a manner  as to be fringed;
 and the moment these divisions are separated here,
 then the animal turns the opposite  way and we
 have here  a  disc with fringes  round it,  turned in
 opposite directions.  We see a cavity forming here.
We see appendages here formed, and we have very
soon a regular medusa! (Applause.)  Thusaftera
series of various formations  we have several dis-
tinct individuals produced from  tbe single egg.—.
The number ot animals thus produced irorri one egg
is sometimes as great as a dozen,  and even more.
  But what i.i very singular in this process is this—
that the upper p...;on of the animal does not undergo
these changes.   The moment the animal  divides
i'jto these numerous young medusa?, this dies  off'.—
T;ie upper portion of the stem dies away, and it is
only the  lower divisions, formed in the manner I
have described, which constitute  new individuals.
  More  extraordinary phenomena are observed in
another type of the medusaB  similar to these.  In a
species little known and not observed  that I  know
of on the American shores of the  Atlantic, we find
a  compound unimal—several individuals being at-
tached to one another and swimmiDg freely in the
water.  They have all the general arrangements of
t;>e medusae. They have been described by nu-
merous naturalists, and two varieties of them have
been noticed.  Chamisso, the Prussian naturalist,
remarked that one variety of these combined ani-
mals had al>vays isolated eggs, while the other had
eggs in bunches.  He was  induced to admit that
these ten types  were of the  same species,  being
only different stages of the same being.  This was
regarded as rather inadmissible, until lately a Ger-
man naturalist named Krohn, in the course of inves-
tigations on the coast oi'Sicily, ascertained distinct-
ly that it was the fact, and that in one and the same
spt-cies there is a set of isolated individuals having
eggs which never separate and form individual
groups of animals, while each individual  of  these
bunches lays isolated eggs, which form free, uncon-
nected individuals.  So then we have successive
generations which do not resemble each other. aDd
in which the grand-parents are similar to the grand-
children, but the intermediate generation never like
that  which  precedes or follows  it!  We have in
mankind  something to remind  us of  this carious
phenomena.  We find family likenesses, as they
are called, go through two generations, omitting the
i  .cermediate.  Certainly that is a corresponding
fact, to this.
  These phenomena  it is  somewhat difficult to
t.-ace, as it  is necessary to follow for a loog  while
the same individual, but they have been ascer-
tained beyond a doubt, and  especially through the
care of the  Swedish naturalist, Sars.   It is singu-
lar, I may here  remark,  that a gentleman should
be found in a country so poor in interesting natural
phenomena ready to devote himself to the minute
investigation of  these phenomena, and succeed in
so eminent a degree.  In some other  portions of
Europe,  on. the contrary, where the  facilities  of
prosecuting such investigations are very remarka-
ble, comparatively little advance  has been made in
natural science.
   The next class of which  I shall speak is the
Echinodermata.
   The internal structure of this class is more com-
plicated than that of tbe preceding, though it fol-
lows the  same plan.   We  have here also the or-
gans arranged  as  rays round the  central cavity.
This central cavity contains  numerous independent
organs. While we had in polyps and  medusas the
function of digestion and respiration produced by
one and the same  cavity branching within the re-
cess of the body, in this class we have an alimen-
tary cavity  forming a stomach and extending some-
times in several circumvolutions  through the body;
and the respiratory function performed by indepen-
dent appendazes.  The fluid is set in motion by
organs always independent  of the alimentary canal
as well as respiratory organs, though all in connec- 
The  Animal  Kingdom.                               15
 tion, and in  connection  similar to what obtains
 among the medusa.
   Many of the facts which I shall add now were
 not fully ascertained until lately.  But recently I
 had an opportunity of studying the internal struc-
• tureof this class while on board a vessel employed
 in the Coast Survey.  I have thus been enabled to
 observe more  attentively the star-fishes, and dis-
 cover how intimately allied  they are  to  the me
 dustrj and polyps.  I may here be permitted to re-
 mark that,  notwithstanding the material which
 is at hand on  the shores of tbe Atlantic for the
 study  of  the  whole of the  types  of radiated
 animals, there  is  no work  existing on  the  po-
 lypi of the  American coast; there is no  work
 in  which  you  can find, even  a  dry  catalogue
 of  this  species.   Though   so  many  beautiful
 works on the Natural History of this country, and
 especially of this State,  have been produced, it is
 somewhat surprising that there is no record what-
 ever of the radiated animals.  There is no work on
 the medusae. These three classes of Radiata afford
 an ample field of investigation, and one which will
 fully compensate the labor bestowed upon it.  It is
 due to the cause of Truth and Science that the pub-
 lic teacher should not only ascertain what is known,
  but also what is to be done ; and here a great deal
  is  to  be done, this group having been much more
  neglected than  others  of the Animal  Kingdom.
  (Applause.)
    The most  admirable arrangement is seen in the
  external  covering of the Echinods-rmata. It will
  scarcely appear credible that these two specimens
  are formed  of the same hard plates, arranged in
  the same manner, only of different proportions, so
  that one presents a sphere-like and the other a star-
  like appearance.  But if in theone case the plates
  were a little elastic, it wouhl be easy to change the
  fonn of tbe  star-li'-h into that of the echinos, and
  vice versa. After 1 have  shown the structure of one
  of these  animals, I trust that this statement will
  not be regarded as at all exaggerated.
    You see t.vo openings in such an animal—an up-
  per and a lower—not always opposite each other.
  1  shall begin  with  the simplest class, before ap-
  proaching the other.  Around this  simple opening
  five large plates are placed so as to leave a space
  between them, and five  smaller plates occupy the
  interstices.  In each of these large plates there is a
  hole.  Through  these five  holes live tubes open.
  Through these the eggs escape.  The plates of the
  body are arraoged  in  a series  of very  different
  kinds. Alternately we have a series of plates per-
  forated and a series of plates imperforated.  Upon
  those plates without holes we have large tubercles,
  upon which  the  tentacles or  spines are  movable.
  These form, as it were, ten vertical ribs from each of
  the openings to the other.  Through the holes of
  one of the series little  tentacles protrude, having
  an opening in  the end, and which can be retracted
  and pushed  out so as to disappear or extend even
  beyond the  points  of the  spines; and  by these
  tentacles the animal can move as well as by the
  motion of the spines. These plates, which are im-
  perforated,  are just oppositeJ;o the  large plates.
  Those  which  are  perforated,  are intermediate.
 They  all  meet  at the lower end, where there is
  another large opening, and this lower opening is
  the mouth.                     .  .     .
    The spines are movable, and it is  their motion
 which  enables the animal to walk from place to
 place.  In some, the powerof locomotion resides in
 the minute tentacles in the plates.
    The food is introduced through the  mouth, and
 is crushed between very powerful plates. You find
 the jaw very complicated.  Tbe complication is so
 great that it would  require a full hour to explain
merely the structure of this part of the animal.—
There is  scarcely any portion of the organization
of the animal creation more complex than the jaw
of these animals.  It is formed of almost  innumer-
able hard plates,  furnished with  teeth,  moved
by  very  distinct muscles, and  put  in  action by
a complicated nervous system.  I  will  mention
merely that these  jaws  are five  in  number,
and are  arranged in such a manner as  to cor-
respond with these ten series  of plates.  One
jaw is always before an imperforated plate. These
jaws  are  so powerful, that they can crush shell-
fishes and the hardest bodies.  The  intestinal tube
is a wide tube provided with several appendages,
bo as to make it more complicated than  in any of
the other radiated animals.
  But what is more singular in these animals is the
existence of a heart and actual respiratory organs.
These tubes, which can be protruded through these
small holes, terminate by a hole, and inside of the
shell there is in each of these tubes a considerable
vesicle which is filled with water, upon which there
is a number of blood-vessels. But here these tubes
can be shut, and there is another apparatus for in-
jecting these vesicles in the tube.  I should  have
mentioned that one of these plates is larger than
the others;  and there is then a sieve of little boles
by which the water can  enter into  the body; and
by another  tube which  comes down in  thatway
and reaches to the lower opening, all these  minute
vesicles can be tilled ;  so  that there is an alternate
movement of the water from outside and through
these tetitaclesand shell to maintain a current upon
the organs which are  covered  with blood-vessels.
Respiration is nothing but an interchange of air
and liquid moved in vessels.   Htre we have all
theae conditions in the interior of the echinos, the
heart being placed near the intestinal tube.
  'Still more, we have  a complete nervous ring
around the jaws and from  five  points of the ring
threads arising and proceeding along the imper-
forated plates so as to reach the upper ridr;e where
they  terminate on the  five smaller plates which
are perforated.  In each of these holes  we  have
an eye, so that we have five eyes at the termina-
tion of those nerves arising from the ring around
the mouth.
   There  are two principal forms of the echinos.
The star-fishes  are one of  these principal forma-
tions,  and  are by no means so simple in struc-
ture as the polyps.  They have a  peculiarity not
easily explained.  The whole body is full of water.
We have a similar general cavity as that found in
the polyp and jelly-fish, but no bole by which the
body could  be  filled.  This hole forms the mouth,
but the mouth and the intestinal tube do not com-
municate with the general cavity of the  animal.
Again:  these  perforations through the  shells,
by which the tentacles  come out, have no  com-
munication  with the internal  shell.  The  ques-
tion,  then,  was—How  does  the  shell fill  with
water?  No opening was  seen.  But   there are
really openings,  so  minute as to  be seen  only
under a high microscopic power; and I have  been
fortunate enough to ascertain that these holes exist.
I have even seen the membraneous tubes which
pump the water and fill the whose cavity of the an-
imal.  These are so extremely  minute  that they
cannot be seen by the naked eye until it becomes
accustomed to  the investigation of them. Then
they are just as plain as  any other part of  the ani-
mal.  But they are extremely contractile,  and the
moment the animal is touched they become retract-
ed and will not be seen for  a long  time.  I  have
injected these tubes with colored matter; and by
keeping the animal in colored fluid, I have demon-
strated that there can be no doubt of the fact of 
16

their being the apparatus by which the water en-
ters the animal.                 ...    ...
  Not *->hstanding all these complications, there is
only one plan in these animals.   All  have one
central cavity, an alimentary canal.   This canal
is either a single sac, or it is an alimentary tube
complete of itself but with an independent system
for respiration and circulation.  But the arrange-
ment  of the  blood-vessels  is  such  that  there
is the  strongest likeness between  it  and  the
arrangements of the circular canal in the medusa.
One and the same plan are apparent in all these
complicated structures.   The  question  is, what
does  such  a  plan  indicate 1   Have  we  here
only material  phenomena, evincing the  influence
of physical causes  in  the  combination of  vari-
ous organs, so  as  to  form a system  more,  or
less  complicated ?   No; we  have more  than
that.   We have a succession of forms which show
a progress.  We begin with a lower type.  We
pass through more complicated types.  .We come
to the very complicated form of the echinos. And,
though these forms are so complex, we find them
in the  same type of animals, in the same climate
and in the same conditions of life.   In all parts of
the world—in  the most different conditions and  in
Prof.  Agassi z's  Lectures.
the most similar conditions—in the arctic, the tem-
perate and the tropical regions—we meet these
varied classes  of the same type, so that the whole
amount of external circumstances in which any or-
ganized being can exist, are acting on these animali.
It would be very unreasonable, then, to admit that
all these varieties were produced by these external
conditions.
  Again: Have we a mere complication of organs in
these animals 7  No.  We do not trace only mate-
rial phenomena. It is not we, who by our investiga-
tions have made these  creatures to agree on one
and the same plan.  They exist on one plan;  and
instead of tracing material phenomena, we actually
trace  thoughts, and  thoughts not  ours—but  the
thoughts of that Mind which created them.  I think
in this way it can be shown by sufficient evidence
that there is an Intelligence which planned these
things, and  formed  and  created them on a premed-
itated plan—a  graduated  scheme of structures
from  the simplest  to the  most complicated; and
that each  animal  was endowed with the power
of so  resisting the influences to which it  is  sub-
jected as to retain its original conformation under
the most diverse conditions of climate and circum-
stances.
LECTURE IV.
The Calcareous Deposits of the Polyps....Why the Polyps cannot be considered higher than the Acalepha....The
   Molliwca— their great number....Recapitulation of the Structural Characteristics of the Radiata....Entirely dif-
   ferent arrangement of Organs in  the Mollusca___Softness of the Mollusca___Contractibility....Nervous Sys-
   tern....Alimentary Cavity becomes complicated....The  Respiratory  Organs.... Structure and Position of the
   "Gills"....Organs of Circulation....Extraordinary Structure of the  Blood-vessels....Theory of the Formation
   of the Blood  and Circulatory Apparatus....Subdivision of the Mollusca___The Acephala.... Characteristics
   of this Class....Mode of ascertaining the Type to which Fossil Shells belong.
  Ladiks and Gentlemen : Since the delivery of |
my last Lecture I have received several letters ask-
ing questions relative to the structureof the Radiata,
which I shall be happy to answer as far as in my
power:
  " Is the carbonate of lime, which forms the coral forma-
tion.secreted by the polyps from the food upon which they
subust, in a way similar to the bones of other animals i"
_  " Are not the Polyps a grade higher than the Acalephae,
inasmuch as we have in them the  first exhibition of bony
structure, which appears more perfectly in the Echinoder-
matae, the next higher grade.'"
  These questions relate to one point—What is the
proper value of the  hard calcareous matter  which
is secreted in the polypi ?   This calcareous matter
has not been long investigated.  In fact, the first
correct work on this subject is to  be found  in the
volume alluded to, forming a part of the Narrative
of the Exploring Expedition.   In that beautiful
work of Mr.  Dana, we have for the  first time the
results of accurate and patient investigation  of this
subject.   He showed what was not known before,
or what at all events was not understood, that the
limestone portions of the polypi form a portion of
the animal, and not mere excretory matter, similar
to shell.   They belong to  the body of the animal
and are not a deposit  of the external  parts of it ■
and in this  respect they  are really altogether dif'
ferent from  the shells of the Mollusca, which are
secreted within the skin.
J0o .xPlain ftt,'y. *« difference, let me enter into
some details relative to the structure of the skin.
ihe skin  m animals is composed of three layers
If wecut through the skin into the body of WanT

SS.Tp,indf,ft a  suPerficial layer composed of
of ve8seunr^dlly 86enu  Fnder thatis a Network
ol vessels and nerves, the latter giving to the skin
its sensitiveness—the sensitive portion of the skin.
Then we have a third layer:  a tissue of threads in-
tricately interwoven in all  directions, forming the
protective  layer.  These three different portion!
have different functions.
  The  external  layer is  constantly reproduced by
blood-vessels, which deposit a liquid in the vessels
already formed  and from  which tbe new vessels
are constantly formed. When the skin is cut we
sometimes see a transparent fluid escape from the
cells and accumulate on  the surface: and this lym-
phatic  fluid, as it is called, is the medium of the re-
production which is always going on.  Now,  in the
Mollusca, the shell  is formed in  this layer  by sac
cessive deposits of limestone, into  which I shall
not now enter as I shall have occasion to go farther
into these details by and by. But let me now men-
tion that between the upper or external coat of
skin, which is called epidermis, there are layers of
limestone in that way by the secreting portioni of
the skin formed of a network of blood-vessels, so
that the shell is formed of calcareous matter form-
ed within  the  skin itself.  Not so  in the polyps,
where the mass of the  animal—the walls  of the
body—secrete within the substance tbe calcareous
portions.  I make here the outline  of a
polyp,  with  its  tentacles: here is the|
mouth, here the walls. Now,  within the
walls,  in the mass of the body itself
there are little  fragments  of limestone
deposited in an irregular  way, entirely
unconnected with each other, which sep
arate in several, but in others unite  tol
form a  porous mass; and these calcareous'
particles are sometimes  formed in such quantities'
as to form an internal framework, covered w
 
The  Animal  Kingdom.
17
•oft parts of the animal. So you perceive thatthere
is not only in the position, but also in the mode  of
deposition of the limestone, a great difference be-
tween the polyps and the shells.
  Again, this skeleton, or this frame of solid parts
within the animal, cannot be considered as identi-
cal in different types.  The skeleton of  the verte-
brated animals is not only carbonate of lime,but it is,
even chemically speaking, somewhat different.   It
is a carbonate and a  phosphate of lime ; and in this
respect there is already a difference; but the differ-
ence is still greater  when we consider the general
arrangement and relative position of the  internal
skeleton of these animals, and the external skele-
ton of the shells, or the internal skeleton of the po-
lyps. In the polyps these solid parts do not protect
any essential organ.   They are within the walls of
the animal, but the  soft surfaces of these walls are
the parts which protect the  intestine and form the
internal  cavity; while the bones  themselves pro-
tect the large  cavities of the higher animals, cir-
cumscribed to spaces in which the brain and spinal
marrow are on one side,  and the alimentary canal,
the heart and the lungs on tbe other side,  are con-
tained. So that these two systems are by no means
to be regarded as identical.  They are identical  on-
ly in one respect. It is'true that these hard parts
protect the  body in general ; but in an essential
point they are different, inasmuch as they  are
formed in a diiierent way, formed  by different por-
 tions of the  animal, and sustain different relations
 to the various internal systems of organs.
   Much remains to  be done in the investigation of
 the corals themselves.   The proper organs of se-
 cretion of those hard parts in  them are not known.
 It has not yet been ascertained in what way  the
 calcareous matter is secreted from the soft parts.—
 There is, then, here also an ample field for investi-
 gation.  Unhappily, this investigation will scarcely
 be attempted on these shores, as there is only, as
 far as I know,  a single species of calcareous polypi
 en the western shores of the Atlantic, north of  the
 Gulf of Mexico.
   The other question—Whether the polyps  are
 not higher than the  acalepbse ?—is answered by it-
 self.  If  the calcareous parts of the polyps have
 not the same meaning as the analogous  parts of
 other types, the existence of such a hard skeleton
 will of course not be a test for the degree of their
 organization.    And again:   we   have among
 polyps themselves,  some with, and others without
 hard parts, and even the great amount of calca-
 reous matter which  is deposited in  many of them
 will never be  a sufficient reason to consider  the
 polyps in any  way higher than the acalephoe, as
 the alimentary cavity is  a simple sac in polyps,
 while it is a branched cavity in acalephaa, perform
 ing at the same time the functions of  a digestive
 tube and circulatory organs.
   __We now enter into another field of the Animal
 Kingdom—into the  study of the Mollusca.
   These animals are very numerous.  The number
 of species which have been collected at this time-
 including those only which are provided with shells,
 —is perhaps six thousand, perhaps even as high as
 ■even thousand; and we may suppose that  the
 whole number existing no w, will not fall short of ten
 or twelve thousand, if we include the soft, naked
 species as well as those  protected by a hard calca-
 reous shell.  The number of species which have
 existed in former ages—in geological times—whose
 remains we  find in  a fossil state in the  successive
strata which constitute the crust of our globe, is
still greater.  It is  astonishing what a quantity of
fossil shells are found in the different strata of the
crust of our globe.   There is scarcely any locality
which has been well examined that does not exhibit
almost as many fossil species as we find on any ex-
tensive  coast of any sea.  Compare, for instance,
those shores which have been most investigated—
the shoresof France for instance—where the shells
from the time ot  Lomarc  up to  this period have
been so  assiduously collected.  There the number
of species known  to exist, when compared with
the number of species, found in  one and the same
stratum of the tertiary deposits  in the neighbor-
hood of Paris, is much smaller.  There are scarcely
eight hundred  living shells found  in the Mediterra-
nean or French shores of the Atlantic Ocean, but
more than twelve  hundred  fossil  shells have been
found in that single stratum—in that limestone on
which the City of Paris is  built, and of which such
extensive deposits exist in the neighborhood.  In
that single stratum is found at this day one-third
more fossil shells than live on the whole extent of
the  French shores!  This  will show how large the
number of fossil shells must be, and  how  large it
will turn out to be, as soon as we have made more
extensive researches in the field of fossil shells.
   To understand properly the  character of  the
Mollusca, it is well perhaps torec apitulate briefly
what I have said of the Radiata; as the differences
between the two  large types is less  in the details
of their organization, than  in the  mode of the ar-
rangement of their organs.  The Radiata have their
organs distributed around the centre.  This centre
is the mouth, and the mouth is turned  either up-
ward.  We have the mouth upward in the  po-
lypi, downward in the echinodermata. Nowhere
have we the mouth on the anterior portion of the
body. Among the Radiata there is no anterior ex-
tremity which prevails over the sides or posterior
 extremity.  All the rays diverge from tbe centre
 and are of equal value,  and when we can trace
some indicationslof a bi-lateralsymmery it is owing
only to  slight differences between these rays, and
 not owing to any  general  arrangement on the  two
 sides of a longitudinal axis.  There is no longitudi-
nal axis proper in the Radiata.
   In the Mollusca we have an entirely different ar-
 rangement. The mouth moves toward one end of
 the animal, and now we have an anterior extremity,
 though we have  not yet a head—not organs of
 sense.placed  always round tbe head.  But there
 is at least an anterior extremity,on which the mouth
 is situated, and  round it  there  are tentacles by
 which the food is introduced into the alimentary
 canal.  Thus the anterior extremity is given by the
 position of the  mouth,   and  the two  sides by
 the general arrangement of the  viscera.   We
 have not only an anterior extremity but we have
 a dorsal region,  a  right  and a left-hand side—
 a lower and an upper region—and in all the Mol-
 lusca those regions can be readily  distinguished,
 though the animal does not  always stand on the
lower extremity.   There are some  who  for their
 whole lives rest  on one side.  For instance, the
oyster lives constantly lying on the left-band side;
 others are attached by the  upper extremity  and
 stand the lower extremity upward,  and it is only
 by  means of comparison  that we  can ascertain
 which is  the right and left hand, and by finding
 where the mouth is placed and by examining the
relative position of the different internal organs.
   The body of the Mollusca is  always very soft
Hence  their|name Mol
lusca,  which  signifies
" soft animals."    The
body is exceedingly con-
tractile.  It can be con
tracted   so much  that
large animals  will occu
py a very small  spa<;e
when contracted.   Fur instance, the animal which
 
18
Prof. Agassiz's  Lectures.
forms this shell, which is, as you perceive, of large
size, and out of which  it pushes a large foot on
which it walks, when contracted is entirely con-
cealed in the bottom of the cavity.  In others there
are two shells which cover the soft parts.  Some-
times there is bnt one shell very much curved on
itself; and in other cases forming only a flat disc,
covering only the upper part of the body.
  The softness of these animals is very character-
istic,  and in no other t.\pe do we find tissues so
sou as in this class and so capable of containing a
great quantity of water.  They continually absorb
a certain quantity  of  water, which penetrates the
mass of the body and maintains it in a ttate of ex-
pansion.  But  when contracting this water, is ex-
pressed in a way quite similar to the water  con-
taini d in the sponge when it is squeezed.
  The organization of the  Mollusca is, ia  some
cases, highly complicated. In others it is as simple
almost as in the polypi. The difference ia the latter
case is only in the s_^ rumetry.  The mouth being in
the anterior region, and the nervous system sur-
rounding the anterior  extremity'of  the intestinal
canal in a  vertical position, while in tbe Radiata
the nervous system is placed horizontally.   The
nervous system is placed above the intestinal ca-
nal,forming a ring around the tube; with  some other
ganglia below, from which tbe nervous threads run
into tbe different organs. From the upper ganglion
we have nervous threads going into the tentacles.
Here are threads going to the other  organs placed
in the cavity of the animal; and here are  threads
running into the muscular fibres which move the
animal.   A similar structure is found in those hav-
ing two valves, only  the symmetry is  somewhat
different.   Always the  nervous system  is  com-
posed only  of a swelling above and a swelling be-
low the alimentary canal from which the  threads
are sent to the different organs.  That  is the gen-
eral arrangement of  the  nervous  system in all
the ollusca ; the Malimentary tube passing through
the nervous ring, but the ring having  a vertical
position, while iu the Radiata it has a horizontal
position.
  We see the difference here is rather in the posi-
tion of the organ—in the relation with other parts
—than in the structure.  This nervous  system is
scarcely any more complicated than the  nervous
system of the star-fish, or  echina.  Perhaps t!iese
ganglia  a?e somewhat larger and  less numerous;
and in the smaller number is evinced a  degree of
superiority. We see in the higher animals that
certain organs not unique but in pairs, in the lower
animals exist in great numbers.  In the  star-fishes
and echina, where we have the first evidence of
eyes,  we have an eye at the end of each  ray—as
many eyes as there are rays, and as many  ganglia
as there are rays, and from each a nervous filament
running through each ray.   Here we have a small-
er number of nervous  ganglia and they  are placed
so that one  stands above the other and on the ante-
rior region of the animal; in that way this ganglia
or nervous centre has a greater influence upon the
whole animal; and it is only owing to the position
of that nervous mass that the anterior region of the
animal has  become more important and possesses
greatervitality; while other organs round the mouth
have a higher importance  to the functions of life.
Wherever the nervous system becomes  larger and
acquires a preponderance over the other organs,
then we see that life acquires greater intensity
and that all the important organs are accumulated.
It is so with the head of vertebrated animals which
contains all the organs of any high importance.__
The organs in other parts of the body are  just as im-
portant to the maintenance of life and the sound
condition of the animal, nevertheless t':ey  do not
 possess the high value  which the organs in the
 head of these animals exhibit.
   The alimentary cavity  is complicated in the Mol-
 lusca.  it is i o longer a simple or branched sac, as it
 is in the Radiata.  But we have in them, behind
 the  mouth, which is  usually surrounded by ten-
 tacles, to  introduce the  food, sometimes  two  in
 number,  and  sometimes four, arranged iu  pairs,
 two above, two below, or only two on the sides—
 behind the mouth, I was about to say, there is a
 narrow tube, the oesophagus, and usually a large
 ba,r which  is the stomach, and the intestine behind.
 Now this  stomach  is complicated, inasmuch as
 there is a liver, a glandular organ united with it;
 and this  liver is sometimes very  large, surround-
 ing the whole stomach,  and secreting a greenish
 dark  liquid, known under  the name  of "bile,"
 which is introduced into the stomach and helps di-
 gestion. This bile, the secretion of the liver, is very
 considerable in all the Mi U nsea.   The liver is some-
 times so large  as to exceed in. size the whole of the
 animal.  It is more than half  the weight  of the
 body.  Sometimes there  are several livers, two
 three or four,  arranged around  the  stomach and
 opening directly into it.
   The organs  of respiration are always distinct,
 and uniformly  present the form of gills.  Their po-
 sition varies  very  much in the  Mollusca,  and
 I will not now enter into  the details of the arrange-
 ment of these respiratory organs, as I  shall have
 occasion to explain the differences which they ex-
 hibit in different types of the great group of mollus-
 ca.  But everywhere these gills are present; and
 when I say everywhere, I do not exclude that class
 which breathe the atmospheric air, which have no
 lungs,  notwithstanding they respire  by air, but
 have gills like  other Mollusca, only  they are kept
 in contact with atmosperic air, and not with water.
 Their gills, then, are not at all similar to the lungs
 of higher animals, and are entirely similar to the
 gills of other mollusca.  What are gills ?  Every-
 where  a blood-vessel divides into parallel branches
 which are  brought into contact with the air con-
 tained either in the atmosphere or in the surround-
 ing water;  these organs are called  "gills."   Some-
 times these blood vessels are  united  by a  mem-
 brane which forms them into appendages of very
 varied forms.  Sometimes they are loose, and then
 they form tree-like branches upon the back or into
 the cavity of the animal.   The gills may be exter-
 nal, as in many Mollusca—internal as in others.—
 8ometimes they are placed in such a way as to be
 used at the same time as  organs of respiration and
of locomotion, acting on the sides of the animal and
 performing the functions  of feet.  Sometimes they
 are entirely concealed in the interior, and the water
 and air are  introduced by  external openings.   We
 see all  these differences  among the Mollusca, and
it is  more important to know these differences, as
they have been made by some naturalists the basis
of the classification of this department of the Ani-
 mal Kingdom.   Cuvier's classification of this great
 group  of animals is  almost entirely  based upon
 the arrangement of tjbe respiratory organs.
  The  organs  of circulation are very  singular In
their arrangement  There is uniformly a heart in
the Mollusca.  But this heart is placed in a very
singular manner.  In some it is placed in the cen-
tre ot the body.  In others it surrounds the alimen-
tary tube, so that the intestine passes right through
the heart.   In others  there are  several hearts
placed in different positions  in the animal.   Some-
times there is  a heart at the base of the respiratory
organs, and sometimes a central heart to supply
 the body.   In  some  cases the heart is very near
the mouth,  and opens into wide cavities containing
other organs.  Nowhere  ia the  circulation more 
The  Animal  Kingdom.
19
unequal  in different animals than among the mol-
lusca.  There are not two families in which the
blood is circulated by similar apparatus, and more-
over there is no class among the  Mollusca where
the circulation is  continuous.   I  will give an ex-
ample: Here is one of the Mollusca, re          i
slug.   It has a large foot on which it wal •      j.
flat shell on  its back, in which the viscera are con-
tained.  From  the heart in this   animal there
originates a large blood vessel running downwards
toward the head, and the blood v longer contained
in this vessel is diffused into a cavity, so that the
tongue and posterior apparatus of the digct.tive or-
gans are actually swimming in  the  cavity full  <>f
blood.  From the  walls  ofthis cavity new tubes
arise, which  unite into other vessels, and thus form
an artery or a  vessel running backward and di-
viding into the body*
   In others of these animals we have the blood-
vessels opening into the cavity which  cont-tins the
viscera and  surrounding the stomach—surrounding
the intestines—and surrounding  the liver,  and then
again absorbed by vessels to be diffused into the
lower parts of the animal.  So that there are every •
where blood  cavities into  which the blood-vessels
open, and from which other vessels arise and diffuse
again the blood into the organs.
   The extraordinary structure of the blood-vessels,
and of the circulation in the Mollusca, has not been
long known. It is the discovery of one of our most
eminent naturalists—the  present Professor of Xat-
ural History in the Jardin des Pla/Ues in Paris.  It
throws most important light on the mode of circula-
tion and of the organs of circulation in the animal.
   How are the  blood-vessels and  blood formed  in
animals, and how does circulation begin? In ex-
amining the egg of a fish, for example, we first ob-
serve an accumulation of red corpuscles, which be-
gin to move  in different directions, but without ves-
sels, till,  after a certain time,  there is  a regular
movement of some of these blood-corpuscles in a
straight direction ; and then they will extend over
the surface  of the yolk and form regular streams,
but always  without  vessels till  tbe vessels are
formed around the  blood, when regular  channels
for the circulation arise from the fact that vessels be-
giu to form arou.nl the corpuscles, similar to what
we see occur after a heavy rain.  When the water
runs over the street, there is at first no channel
for the water; but after it has run for some time in
different directions, chanuels begin t > present them-
selves, which gradually become deeper and deeper
in the softer parts, till the water remains bounded
by them.  So in a living  animal, the cells, being
excited by the current of the blood, are gradually
formed into channels.  The younganimalis formed
entirely of cells.  Some of these cells become mov-
able and are moved iu different directions and form
little streams—little currents in different ways, and
then after these streams have  become regular the
vessels are formed  around them.  In this  way you
have a full  explanation of those large blood cavi-
ties in th e Mollusca; and those unconn ected blood-ves-
sels opening into the larger .cavities  and a heart
which is central, but which does not communicate
with the most distant portions of the body. I think
the  only  way  to  understand  the  circulation
is  to   consider  it and  the  blood  as  arising
from the liquefaction, as it were, of the cells which
form the animal, which then become movable, un-
dergo  amotion  in  precise and uniform directions,
and then are surrounded by cells  which  form the
vessels, and which form the heart.  It is only when
tracing all these phenomena  in  the  young animal
within the '  :g that these details can be understood.
But I could  not help adverting to  the  formation |
of the blood-vessels  when speaking of a class in
 which the circulation is so unique as it is in the
 Mol usca.
   Let us cow turn our attention to the M"lineca
 themselves, and see what form  they show in *he
 whole range of the cla«s.   All the diagrams on the
 wall belong to that class, but you  will perceive
 that they .present many different terms.  Here is an
 animal resting on a stem.  There is one very like
 a coral.   Here is one which  for  a  long time has
 united with the coral,  and by many naturalists is
 ranked as such.  You perceive that it  bas  cells
 similar to those of the common coral.  Here you
 have  animals  with  two  unequal  valves.  Here,
 others with two equal valves.  Hr re one with one
 central valve iurved.   Others without any protec-
 tive valve. All these diversities exist in one and the
 same class.
   The Mollusca have been divided into three classes.
 The first class is the Acepknla—animals without a
[ head.  They really have no  head.  The  anterior
[ and poster; ir extremities hardly differ.  This class
 of acephalte have  tiie  bivalve shells.  You  have
 here examples of them; two shells united in the
 superior margin and movable along the back.  But
 many of them unite to form  compound  masses.—
 Yet the organization of the individuals thus con-
 nected has  been  ascertained to show the same
 structure as that of the  bivalve class. I shall soon
 enter upon the  derails after I have  explained the
 characteristics of the acepbalse.
   The characteristic of this class is to have two
 symmetrical regions; a right and a left side, over
 which hang the respiratory organs.   If I cut across
 an oyster, I find that the vertical line is l<m_'t-r than
 the longitudinal diameter.  Here is the  ;\:.trM-iorre-
 gion of the ay ster—here the posterior region : and
 >ou perceive that the vertical or perpendicular di-
 ameter is greater than the longitudinal diameter.—
 Here we have the  interior  mass of viscera,  the sto-
 mach ; and here are both sides, the membranes
 covered with blood-vessels, wiiicb are the gills, two
 oii each side.  That is the  general character of the
 acephalse, to have the gills surrounding the alimen-
 tary canal, the liver and other organs which are in
 the centre of the animal; and over these .-e metimes
 onlv one pair of gills ; over  that, again,ai>k:.i, which
 lines tho shell all over iti internal surface, which
 has been  called 'the mantle."  This arrangement
 of parts is the general structure of bivalves or ace-
 phalous  mollusca.  This "mantle" is  sometimes
 open tee whole length  of the animal.  So it is in
 the oyster.  Perhaps there is no animal  among the
 Mollusca so interesting in its structure as tbe oys-
 ter.  [Here the learned Professor explained a dia-
 gram illustrative  of the structure ot tbe  oyster,
 which, with  t^s  other diagrams, will  be given
 hereafter.]
   Allow me a few minutes beyord the hour, which
 I see has now expired,  in order  to  finish  the de-
 scription of the acepbelae.  (Applause.)
   The shells are not always s_\ mmetrical.   Some-
 times that of the right-hand sick- is larger than that
 of the left-hand side,  and vice versa.   Sometimes
 the anterior and posterior extremities  are equal,
 while the two sides are unequal.  Sometimes, on
 the other hand, tl>e two sides are equal and the
 extremities unequal, and  in  these differences we
 have characteristics by which a great number of
 these bivalves may be divided into families.  It is
 important in the beginning to give them the same
 position when we desire  to compare them. For
 instance, in 6oroe of them  'we have one valve con-
 vex and the other flat.  Many naturalists have con-
 sidered these cases to present instances of a dorsal
 valve and a ventral valve.  But when we examine
 the formation properly,  it  is easy to perceive that
 this is an error, and that what was called the dorsal 
20
Prof. Agassiz's  Lectures.
valve is nothing more than an exaggeration of this
form which we see in the oyster, where one of the
valves is deeper than the  other and is flat.  The
only difference between  the terrebrachela is that
in them the anterior and  posterior margins are en-
tirely symmetrical,  and  cnly the right-hand and
left-hand sides  are unequal. It is not so in the
oyster.  It is important to understand this point.
   Let us take a symmetrical bivalve shell and be-
gin with that.  In that the right and left sides are
easily known by the positions of  both,  by the
appendages round the mouth and the symmetry of
the valves.  There are two equal valves—one on
the right, the other on the left.  Here is the mouth.
Here is the back.   Here  is the foot by which the
animal walks, protruding between the two valves.
Here are the tubes by which the water enters.—
You see that the anterior end of the animal is broad-
er than the posterior, and in every respect it is ea-
sy to see the proper position of such  a shell.  In
the oyster these anterior and posterior ends are so
irregular that we have no means to ascertain which
is the anterior  and which the  posterior until we
open the animal and discover the position of the
mouth.  There we see that the mouth  is between
the two shells here; that the long diameter is the
vertical diameter;  that this  is the right valve and
that the left valve, the valves being unequal, one
convex and the other flat.  But in the terrebrache-
la we have the right-hand valve convex and the
left-hand valve flat, but the anterior and posterior
edge cut precisely in the same way—and thus the
extremities are  so precisely symmetrical that the
blood-vessels which you  see in the anterior  and
 posterior half are distributed in the same manner
 and that there are two hearts, anterior and posteri'
 or, so that if it was not for the position of the month
 and the direction of the alimentary canal, it woald
 be impossible to ascertain that this was the anteri-
 or extremity and this the posterior extremity of
 the animal;  this the back and this the foot.
   Anotfler important peculiarity is this: that tha
 mantle lobe which covered the internal portion of
 the shell leaves a deep impression  on the shell
 from the action of the muscular fibres by which it
 is attached to the shell; and as there is a long tabs
 by which  the  water is  introduced  between the
 valves in some of these animals, and which is re-
 tracted and introduced between the valves, a lares
 sinus is formed.   Thus, on opening a shell, you
 can ascertain whether the animal to which it be-
 longed had this tube or not, by the absence or ap-
 pearance of this sinus— the impression  of  the
 tube.  When the tube, or " siphon " as it is called
 has been long, the impression is considerable; when
 short, the sinus is not so marked.  This difference
 is important,  because  in the examination of fossil
shells, these  impressions  constitute the great test
by which we ascertain the character of the animal
which  occupied  them.  It is in this way that an
idea has been formed of the animals which occupied
the fossil shells, almost as  precise as if the animals
themselves were before us.  The only difficulty is
to compare a sufficient number of types in order to
become completely  acquainted with all the varia-
tions and relations of those parts,  and to trace the
analogy with accuracy and success.
                                       LECTURE  V.

The  Anatomy of the  Oyster....The  Ligament....The Mouth....The  Gills....The Stomach, Liver, Ovary and
   Heart-Position of the Oyster....The Fossil Bivalves....Important considerations relative to the Symmetry of
   the Bivalves....Order of Succession....The various Groups  of the Acephalae....The Shells of  comparatively
   little Importance... .Changes m the Classification ot the Mollusca and other Animals... .Tribute to the Labon of
          CLASSIFICATION OF THE MOLLUSCA.

  1..Acephela..............(Without head.)
       1. Bryozoa..........(Moss animals.)
       2. Tunicata.........(Having a coat.)
       3. Brachiopoda......(With feet like arms.)
       4. Monomyaria......(With one muscle.)
       5. Dimyaria.........(With two muscles.)

 II..Gasteropooa..........(Feet below the abdomen.)
       1. Phlebentera.......(With branched intestine.)
       2. Trockoidea........(Trochus-like.)
       3. Buociwoidea.......(Buccinium-like.)
       I. Pulmonata........(With aerffl gills.)

III..Cephalopoda...........(Feet round the head.)
       1. Sipiodca...........(Squids.)
       2. Naut'doidea........(Nautilus-like.)
       3. Ammonitidea......(Ammonites-like.)

  Ladies and Gentlemen :  After having given a
general outline of the characteristics of Mollusca in
the last Lecture, I proceeded to illustrate the peculi-
arities of the first class of that group called acepha-
la.  Then having entered into as many details as
possible with regard to their structure, I alluded to
the different groups which belong to that class,
but as perhaps many or some of this audience mav
wish to know how these facts are  ascertained, I
have brought here some of these animals in order
to demonstrate in them the  peculiarities of their
organization.  For, let me  remind you that the ob

S3 EEST afe n°tBTeenuas *ou «■ *«J d3i£
™i?fte diagrams.  In the diagrams the objects
must be  represented of  larger size  than  natural!
 and in strong outlines.   Things are not so easily
 seen in Nature, and therefore I wish to show you
 in what manner we must proceed  in order to see
 foi ourselves the objects in nature, and how we are
 able to proceed in making new  observations and
 comparing the types not yet understood.
   I have thus taken for example the oyster, as it is
 the most common of this order of animals.   I have
 been told that there was some misunderstanding in
 the minds of some of my auditors, when I explained
 the difference between the oyster and the common
 bivalve shells.  The misunderstanding was with
 respect to the shell which is concave, and arose from
 not attending to the manner in which the shells
 were held  in the hand when  demonstrating them.
 The two valves are united at one end by what if
 called  the  ligament.  It is  an elastic substance,
 which  contracts when the muscular power of the
 animal which closes the valve is relaxed. In order
 to open an  oyster, particularly for anatomical in-
 vestigation, it is only necessary to pass a knife be-
 tween the valves on the back, near the projecting
 portion, where the two valves are united, so  that
 the strong  muscular portion  of the animal, and
 which  passes  across the whole body and fixes it-
self to  the valve, be divided.  You  see this  dark
spot in the centre of the valve. Here is the ma-
cular portion, tough like meat; and the fibres ot this
part of the  animal are transverse, running from one
valve  to the  other.  Now  after  the valve « «■ 
TJie  Animal  Kingdom.
21
 moved in such  a manner—it is not much matter
 what valve  is  removed, only perhaps it is  more
 convenient to allow the  animal to remain  in the
 deep valve,  which retains the water—you see at
 once the animal in its natural position.  Here jou
 have this muscular  portion,  which is  the toughest
 part of the animal, and then  a skin which runs all
 around the shell. This skin which lines the whole
 inside of the valve, and  which can be upheld very
 easily, is attached to the muscle, and runs all round
 the shell to  the margin.  If  it appears now not to
 cover entirely the surface of the shell, it is owingto
 the contraction of the  fibres which are  in this mem-
 brane.  The margin of the membrane itself  has a
 very complicated structure.  There  are  fringes,
 sometimes most beautiful a'nd of very elegant color,
 in the different species of clams and bivalve shells
 and when you  remove  this  portion  of  the  shell,
 which is called the " mantle."  you have  another
 membrane quite similar to that, which is situated
 transversely.  This is the gill.   There is  another
 inside—a second one, so that there are two lobes of
 the gill on one side ; and  above that two long tenta-
 cles,  which are placed here  above the mouth.  On
 the other side we have  the  same structure.   Now
 the mouth is here on this upper portion of the shell.
 All  that may be more easily seen when you  keep
 tbe whole animal in water, as then, with a brush or
 pencil, you can elevate the  one above the other,
 and examine their beautiful  structure.
   Iu this upper portion  of the animal is the stom-
 ach,  a  large cavity surrounded  by a dark brown
 colored  liver, which forms the softest part of the
 oyster.   Around the liver is the ovary.  The eggs
 are so minute as not to be perceptible to the naked
 eye, but are readily seen under the microscope.—
 The intestinal tube,  which begins here between
 the tentacles, at the anterior portion  of the body,
 turns twice  between the liver and the ovary, and
 then passes through the upper region,  in which we
 see  the heart of the oyster.   The  intestinal canal
 does not pass through the heart of the oyster  as in
 other animals, whicn I shall demonstrate immedi-
 ately.  What is peculiar to  the oyster is that the
 "mantle" is open all round.  There is no siphon,
 but the  water, as often as the shell opens, can reach
 immediately the whole surface of the gill—the food
 can immediately reach the mouth, so that the ani
 mal has no need of a tube which could be elongated
 and  protruded between the valves in order  to ab
 sorb the  surrounding water.
   You see that the position of the mouth indicates,
 without any doubt, that this is the anterior edge of
 the oyster; and this the superior; this the interior
 side ; and this the posterior.   As I have remarked
 the animal rests forever on tbe deep valve; so that
 when examining an oyster anatomically, in order to
 compare it with other shells, we must put it in a
 position different from that it used to have in nature.
 But  this is  the case with  many  other animals.
 Among  the water-insects, for instauce, there are
 many which constantly swim with the feet upward,
 but nobody  when comparing them  with others
 would think  it proper to compare them in that re-
 versed position.  We must in these cases bring the
 animal into  the natural  position of the greatest
 number of animals in order to come to a right un-
 derstanding  of  the  correspondence  between  the
 parts. So it is with the common hard clam.  Thus
 the two valves are precisely identical  in shape —
 But  after having removed one  of  them you  see
 a great difference tn the  structure of the animal.
 There are two muscular  bundles uniting the  two
 valves; one on the anterior  and the other in the
 posterior  portion of the animal, so that the  two
 valves are shut by twosetsof muscular fibres,  and
not by a central set as in the  oyster.   And these
two sets of muscles are placed one on the anterior
and the other on the posterior end  of tbe animaL
Those two muscles act, however, in the same man-
ner as the single muscle in the oyster.  The mantle
here surrounds the shell precisely in the same way
as in the oyster, but it ia not open all around.  Here,
about two-thirds backward, the  mantle unites from
the two sides.  It is open only on the anterior ridge,
so that the water can enter either  between the
mantle lobes or through the hole which is formed by
tbe junction of the two portions  of tbe mantle.
  If, as I have done here, you remove the mantle,
you see similar flat membranes, which are the gills.
They  are so  collapsed in this animal that I cannot
show them. They shouldbecovered with water, and
those who wish to see their structure may remain
after  the Lecture, and I shall put tbe animal in
water and demonstrate these membranes.   There
is a considerable muscular mass,underneath which
is the muscle or foot by which the animal walks.—
This foot they protrude between the valves, and by
means of it fix themselves on the sand or stones and
creep along by successive contractions and expan-
sions of their body.  In the same  way as  in the
oyster, we have here the mouth surrounded by ten-
tacles.  The liver is above, and of a brownish color,
as in the oyster.  Then we have the heart here, be-
tween the gills, and the intestinal cavity,and the ali-
mentary canal which passes through  the centre of
the  heart.   The beating of  the heart can  be
seen for a long time  after you open  the valves of
the oyster. It beats seven or eight times during a
minute.  In the hard clams the pulsations are  al-
most the  same in frequency.   When contracted,
the heart is of very small size—when expanded, it
is three times as large.   This operation of the heart
may be very  easily  seen  if you put the animal
after you open it in the water, so that all the parts
expand.  Here the two valves are symmetrical, and
the anterior extremity differs from the posterior.  I
have already alluded to this fact.but I want to show
one thing more about them, as  it is  important in
order to understand the gradations  among the bi-
valves ; and to understand the reason why so much
importance is  put upon the question  how the ani-
mal stands or lies in its natural position 7
  We  have seen  that some  of the distinguishing
characteristics of the Mollusca are, to be symmetri-
cal, to  have a longitudinal axis and an anterior ex-
tremity at which the mouth is situated.  But what
is singular, these animals in their organization do
not yet stand so high as to assume a constant posi-
tion of the sides of the body.
  The anterior extremity is constantly marked as
the  anterior, the prevailing portion of the animal;
but the sides of the animal, the posterior  extremi-
ties are sometimes lying on the right or on the left,
and sometimes even uplifted in a very irregular way:
  Now, lieio we have a uimive wan t*o symmet-
rical shells.   Here is the ligament uniting the two
valves, and here some tubercles on the edge of the
valve which are usually  but incorrectly called
teeth.  They are  by no means teeth.  They are
merely serratures or dentations.  Here is the mar-
gin of the shell by which the two valves unite more
strongly ; this portion of the shell has been called
the hinge. 
22
Prof. Agassiz's  Lectures.
   Now this being the  anterior extremity  where
 the mouth is placed, this will be the posterior ex-
 tremity, and we will have an animal walking with
 the aid of its feet in an  upright position, the mouth
 forward, the feet downward, the right  and  left
 hand  in an equilibrium  on  the  right  and  left
 hand side  and the  back upward—the  posterior
 being  backward.  But in  the oyster, when the
 two parts  are compared  with  one another,  in
 such an animal we will find that no  longer is this
 position maintained, but the animal through  life
 lies flat on one side, from the beginning.  Th&young
 oyster lies on one side of the egg; begins to grow in
 that position and never comes to have the anterior
 extremity forward and  the sides in equal position.
 One side, the left, remains below, and tbe right in
 the form of  a cover upward, resting upon the lower
 side.
   Now, in the oyster, the anterior and posterior mar-
 gins of the animal are not equal; nor are the right
 and the left valves equal.  Here we have inequali-
 ties between the two valves, and these inequalities
 are very great—not only  are the two valves very
 unequal, but  you  see the  anterior  edge  car-
 ried  forward—the posterior edge  is emarginate.
 Now, we have other bivalves where one valve is
 very deep and the other flat; but where the extre-
 mities  are identical.  They are called the Brachi-
 opoda.   It  is very important  to  ascertain  these
 facts, because they point to a most extraordinary
 circumstance—it is this: that in  shells  found in
, strata  forming  the crust of our earth, we have
 none which have  the two valves unequal.  There
 is not one bivalve shell  with equal valves in any of
 the ancient strata.   There was not one of the an-
 cient bivalves which had this bilateral symmetry
 in its shells.  All  belonged to that claps where the
 two sides could not yet be equalized and stand up-
 right, and of course we must consider  them as of a
 lower grade than those where the symmetry is en-
 tirely perfect.
   There is even something more.   We have  not
 only the valves unequal, but the anterior and pos-
 terior extremities  unequal.  Though these valves
 are still unequal, there is still an approach  to a dif-
 ference between the anterior and posterior extrem-
 ities. The anterior extremity curves forward, though
 the posterior does not yet extend backward.   But
 the fact that there begins to be an equality shows
 that these stand  above those where  the anterior
 and posterior extremities are precisely identical.—
 Now again, those which are  terrebrachela, which
 have the anterior and posterior ends precisely iden-
tical  and the valves unequal, are the oldest. They
fill the strata below tbe coal, and in the coal.  We
have not yet any of those which have unequal
valves,  with  unequal anterior and posterior  ends
before we have passed the epoch of the coal.   So
we see a gradation of the animals in each series,
corresponding precisely  with the order of  succes-
sion of animals in time.  Thus the great importance
of understanding these facts, which at  first appear
to be rather insignificant. But, you see, when I at-
tempted to show that there was a difference in the
actual position of the animal in water, how it stood,
or lay, I expressed thelawof succession oftypes, the
law of gradation of organization from  the earliest
appearance of organic life up to the present time.
Of course, theoldest types once introduced have not
been allowed to die out.   We have in a living state
geveral  brachiopoda, but very few, perhaps one-
fiftieth of the whole number, of the acephalae.  We
have of these bivalves agreatnumber.but they begin
about the middle age of the history of our earth, and
the number is about equal to  the number ot types
now living.  Now the symmetrical bivalves are the
jnost numerous living in our days, and those which
I occur only in the upper strata of the  crust of otn
| globe, which begin in the last time, as it were, the
 last historical and geological periods.  Of course
 there are some few  species  which run through a
 greater range of geological time.  I give only a gen-
 eral outline of this succession, in order to show the
 importance of this thing.
   Perhaps it would be more attractiveto enter into
 details of the mode of living of these animals, their
 uses, habits and so forth;  but these things may be
 found in almost every text-book, while anatomical
 details and these more general bearings of tbe struc-
 ture, with geological phenomena, are scattered in
 isolated papers, and some of these views have only
 be*en  known for a short time, so that perhaps it is
 more advisable to stick  to this point of view rather
 than what is usually called the history of these
 animals.  (Applause.)  It will of course  be per-
 ceived that this difference between the bivalves is
 less important than has generally been considered.
 Whether the mantle be united with the whole
 length of the animal, and whether it be opened for
 a greater portion  is of less  importance than many
 conchologists have thought.
  And again, whether  such an animal has a hard
 shell or not is of trifling importance.  We have, iu
 fact, a great number of animals, quite similar in
 their structure with the  bivalve shells, which have
 no shells at all—and have only a membraneous cov-
 ering, and it is according to this difference that the
class of acephela? has been divided into the follow-
ing groups:
  First, the Bryosoa.  These resemble the polypi
in size.   In these the anterior end of the animal is
surrounded by a circle of tentacles, and  these have
cilia all  round, by which they can introduce the
water. Withiu this membraneous covering of the
animal, is a structure quite  similar to the shell of
the oyster.  Sometimes  members  of  this group
have calcareous stems like the coral.
  Next we have the  Tunicata.   They have mere-
ly the opening for the introduction of the water  to
the gills and the mouth.  It is like an oyster with-
out shells, where  the skin  is entirely  united the
whole length of the animal:
  Then there is the Brachiopoda,  with the  valves
unequal, but tbe anterior and posterior extremities
symmetrical.  Here is the hole through which these
animals protrude a ligament which is used as the
means of attachment.  These  animals constantly
lie upon the fiat valve attached  by  this ligament,
which passes through a hole in the larger valve. It
is this type which is the rrost common, and in fact
the only one,  found in ancient strata  All the lime-
stone and coal strata in the United States contain a 
The  Animal  Kingdom.
23
great number of these  bivalves which are very
well known to conchologists:
  Here we have the type of the oyster—the Mono-
myaria.  These have unequal valves and are also
unequal in the  anterior and posterior sides,  and
bave, as their name imports, a single muscle  run-
ning between the valves.
  The last group is the Dimyaria.
  I have taken up' this view of the subject in order
to impress the audience with the importance of an-
atomical investigation with reference to successive
types during geological epochs.  It shows that there
is a plan successively realized in Nature ; and that
the types now in existence were in view at the begin-
ning.  Such a series cannot be realized, unless at
the beginning, the termination of the plan was al-
ready sketched out.  If it were otherwise, then it
would be precisely like one sitting  down to write
a book without having formed his plan.  If he does
not know where he is to go, how can he ever come
to an end? (Applause)
  We next come to the class of Gasteropoda, the
name being  derived from the large  muscular disc
by which the animals creep.  Here  it is a flat disc
of muscular fibres which contract successively and so
move the animal.  What is very singular is that
some of these animals are able to walk against the
air when swimming at the surface of the water.—
It is necessary to explain  that in order to make it
nnderstood:
   Let this be  a wactsr-basiu, ana ine level of the
 water above.  We have here the pressure of the at-
 mosphere upon the water.  Let now a fresh-water
 mollusc of this class be placed at the bottom of the
 vessel in this position.  It will rise to the surface
 bv expansion.  It will diminish its  own weight
 ■o much that the animal will  rise  to  the surface.
 How is that possible ?  The animal sinks because
 it is heavier than water.  But its weight is sonear-
 lv equal  to that of the water that the moment it
 assumes a larger size,  by dilation, it displaces a
 greater quantity of water  and becomes therefore
 fomparatively lighter than the fluid,  and by this
 process it slowly comes to the surface of the water.
 The moment it contracts it of course again sinks.
 When at the  surface of the water the feet will be
 upward, and by the contraction of the feet the pres-
 sure of the air upon the water is a sufficient resist-
 ance for this animal to walk along on the surface
 of the water, and any one may have  the pleasure
 of seeing  this by observing the motions of any  of
 this species so  common in all our fresh-water
 nonds.  Nor is the motion of tins animal very slow.
 I have seen some not  more than half an inch m
 length walk a foot in this way in a minute.  Ibis
shows  that the resistance must be considerable.
  All the  gasteropoda have that muscular disc at
the lower portion of the animal, and have been so
called because the disc is below the visceral cavity
or abdomen.
  Here I take occasion to remark that masy impro-
per names have been give to animals of these lower
groups, because the animals themselves have not
been sufficiently understood.  Still it is perhaps ad-
visable to retain the names, as if the mode of classi-
li■■■■-.■*•■•! were to be changed to meet every fresh ac-
cession to our knowledge, the memory would  be
embarrassed and endless confusion be produced.
  Most of the gasteropoda have the body covered
with shells; but a great number of them are naked.
Here are some very beautiful from the variety of
their colors.  The size and thickness of the shell
vary very much.  In some  the shell is so minute
that it  covers only a small  portion of  the animal.
In others the  shell is entirely concealed in the skin,
and is seen only when the skin is cut open.  The
shell cannot be considered as a very important part
of the  animal.   There are almost as many of  the
Mollusca destitute of shells as there are possessed
of them.   Again:  all those without shells had
them when young.  If the shell  were of as great
importance as it is generally deemed by concholo-
gists we would not see  so many of these animals
naked.  Though very beautiful and diversified, the
shells, then, are of comparatively  little importance.
  Yet the shells after all are not without their value
in the study of Natural History, for it is  by means
of them that we can study the Mollusca of ancient
geological times.  In a fossil state there have been
found a great many of these univalve shells.  But
we do not  know how many or what sort of naked
shells existed in those epochs simultaneously with
the others.   It is only from those which had a
hard coat that we can form an idea  of the gaster-
opoda of ancient times.
  The shell of tnis class is  often a single flat disc
without any  circumvolutions.  In  that  case it is
formed  of successive layers,  growing  larger  and
larger,  and forming concentric  lines  as you  see
here. The mode of deposition of this  shell is in
this way :|
  First above the animal there is a small  calcare-
ous disc.   Then, as it grows larger, the mantle se-
cretes another layer,  a larger layer, and another,
and another, each still larger, and so the shell grows
in proportion as the animal grows.  Now in several
this disc is flat.  In others it is more or less conical.
Here is the beginning of  a cavity into which the
animal can retreat. In some it is even a deep cone.
In some the cone is so high as to be like a cylindri-
caltube.  But usually this tube is  rolled  up, and
that in  a very peculiar manner.  Sometimes in roll-
ing it will form a few circumvolutions, and you have
an apex.
 
24
  In some  the  circumvolutions  are  very  nu-
merous, and succeed  each other in such a way as
to form a high spire, and you easily understand that
that is a mere tube rolled in a spire.  Sometimes
the tube thus rolled turns  to the right—sometimes
to the left.   But what is remarkable, all  the indi-
viduals of a species which  is designed to be rolled
up to the right are turned the same way, and per-
haps of thousands and tens of thousands  you will
not find more than  one reversed.  These reversed
individuals are highly prized by collectors ot shells.
They are  extremely  rare.  Among tbe  common
snails we find perhaps more of these reversed shells
than in any  other class.  What may be the cause
of this constant rolling in one and the same direction
is not known.   It begins in the egg.
  The opening in tbe shell is generally  circular.—
In some cases it is oblong. In some it has a notch,
and through that there passes a membraneous tube,
through which the  water is introduced and reaches
tbe respiratory organs.  Here is a case in which
this prolongation forms a kind of siphon, protecting
the membraneous tube. An animal with such a tube
can breathe without moving its body. Those which
have a circular opening are obliged  to  come out
when they breathe.  Sometimes the membraneous
tube coming out of this notch is very long, as long
as the shell itself,  and forms a kind of horn, rising
above the animal.  Many of this class become blind
when they are full grown.
  The mouth is usually surrounded by the tentacles
and is at the anterior part of the head.  But some-
times there is  a proboscis, a long tube, at the end of
which we have the mouth.
  In  some, on the contrary, the mouth is very
short,  and  in  such the  proboscis protrudes.  In
this respect there is  a  great variety, as  there  is
also in the form and shape of the foot and mantle.
In some the foot is much broader than the shell, so
that when you look on the animal from above, the
shell does not seem to be  more than  half the size
of the foot.  In other cases the foot is so large that
the  shell  and  head  of the animal constitute the
smallest portion.  In this  respect great  diversity
exists.
  Again, in some the mantle is so broad that it will
cover a portion of the shell by folding itself back-
ward, thus concealing  the greatest portion of the
Prof Agassiz's  Lectures.
shell, and we have cases where the foot is of an
amazing size when compared with the size of the
animal.   All these differences are important,  as it
is owing to some of them that concholog sts have
divided tbe gasteropoda into several classes.
  One is that class called Phlebentera, entirely na-
ked, and peculiar for the structure of the intestinal
canal.  Their name indicates that peculiarity. The
alimentary canal forms a kind of circulation, and in
this respect this family does not stand much higher
than some of the medusae, but they differ in the
respect that the alimentary canal has a longitudinal
axis.   They  have, all  of them,  external  gills,
sometimes most beautiful, forming bunches of blood-
vessels hanging outside, which are used  as oars
and constitute  the means of locomotion.   The
modes of locomotion are either by the feet creeping
along or by the  gills in swimming.
  There is another group rather interesting, which
 contains animals of so greatly varied appearance,
that to one accustomed  to combine animals ac-
cording to their general appearance,  it  seems
unnatural to  classify  tbem in  one family; but
they have been so classified  by so high an au-
thority in Natural History that no one has dared
to  alter  the  classification.  A  Swedish Natural-
ist  has proposed a modification  of the classifica-
tion of Cuvier,  and indeed it is quite reasonable to
suppose that  as tbe investigation  of Natural His-
tory proceeds, and fresh discoveries are made, mod-
ifications of classification will become necessary.—
Nor does it in  the least  reflect upon the exalted
character of the great Naturalist I have named, to
whom tbe science owes so much, that these changes
should be deemed necessary. It has perhaps been
owing to his immortal  work that scientific  men of
our day have been able to improve the methods of
our earlier naturalists.
LECTURE  VI.
Remarks Explanatory of the Lecturer's Views with regard to the Succession of Animals in Geological Times
   Views entirely different from thote advanced in the " Vestiges of Creation"....Character of that Work....Clasai-
His
fication of the Gasteropoda not Natnral... .The Trochoids___The Pulmonata.
Peculiarities in the Organization of these Animals....Fossil Shells.
.The " Cuttle-Fish"___Interesting
  Ladies and Gentlemen :—Several questions
having been put to me with respect to the views
which I entertain in regard to the development of
organic life, and some observations having been
made with respect to the tendencies  of the facts
presented in my Lectures, I deem it necessary to
explain what I understand, in reference to the suc-
cession and development of organic life.
  Tbese words are  constantly  used  and  some-
times in very ditlerent senses, so that there is in-
finite misunderstanding among  those who use the
same words and mean very ditlerent things by them.
  When we speak of what comes later  we of
course have referencer ^vhat comes before. We
will take for illustration ..ne chick.  From the time
when the egg is laid  to  the period  when the ma-
ture  chick  is  batched,  a succession of changes
takes place.  This epoch between the formation of
the chick and its full growth is called its develop-
ment, and the changes which such an animal under-
goes during this time are its metamorphoses.  We
have  often limited tbe meaning of metamorphoses
to the changes which we perceive in the butterfly—
in the caterpillar, where these changes are inter-
rupted and  are very striking. Everybody knows
that a butterfly is formed from a caterpillar out of
an egg.  The caterpillar, or worm like animal,  af-
ter it has grown to a  certain size undergoes a
change—it  assumes  a  new form, that of  the
chrysalis.  It is motionless and so  remans for a
certain time, till out of this comes a living butterfly
with all  its brightness and vivacity  of life.  Now 
The  Animal Kingdom.
25
these changes have usually been  called metamor-
phoses, although not so striking, nor interrupted in
■uch a  manner as to form distinct ages in tbe life of
the animal.  They pass from one to another, and the
early state ot the chick,  for instance, is so .dissimi-
lar to the full-grown chicken that noone recognizes
them if they have a chance to compare them.   But
il we can trace all the intermediate stages we find
that they are  connected  in such  a manner that
there is no interruption  to the succession of these
changes—and thus we do not in that case usually
speak  of metamorphosis but  of development, and
■uch a development is also called  the  progress of
an animal during the  different  stages of tbe  egg.
In a metaphoric manner we are also  accustomed
to speak of metamorphoses in the Animal Kingdom
through different ages of geological time.  Every-
body knows that the earliest Geology has been made
so clear that I suppose all  know that the strata
which form the  crust of our  globe contain  a
great  number  of  fossil remains—remains of fossil
beings in all classes of  the Animal Kingdom—and
when tracing the whole  succession of these animals
we find that the most ancient strata—those which
form the lower beds of this crust of the earth—are
different from those which are found in the interme-
diate beds,  and which differ again from those found
in the uppermost beds.
   Now in this  succession of strata and of animals
through the whole range of geological  epochs, we
have what is considered a progress.  We find that
the  types in all the lower  beds resemble tbe  lower
types  of the now  living animals.  For instance, I
have mentioned that the  Brachiopoda among the
Mollusca are the most ancient acephala. We find
among the vertebrated animals that fishes only are
found in the lower beds.  There are no reptiles, no
birds,  no mammalia, nor any of the higher classes
of the Animal Kingdom. And here, again, we may
■peak of a progress in the succession of types.  We
can speak, also, of a metamorphosis in the Animal
 Kingdom, but not in  the  same sense in which we
■peak of the metamorphosis of an animal; because,
when we have a butterfly arising from a caterpil-
 lar, then we have  one and the same animal contin-
 ually  living  without  interruption, and passing
through successive changes ; while, when we speak
of the  metamorphoses of tbe Animal Kingdom of the
 different classes—when we speak, for instance, of
 the metamorphosis of the class of Acalepbse, and
consider the Brachiopoda,  Monomyaria and Dimya-
ria as different stages of this metamorphosis, of
 course we  would have  here a succession of differ-
 ent types, different  animals, unconnected  mate-
 rially—not the same living beings undergoing these
 changes, but a number of distinct individuals un-
 connected with each other, not derived from  each
 ether.  Nevertheless, there is in their succession a
 great analogy—a striking analogy, with the changes,
 the progress, the development observed in one and
 the same individual while growing from the egg to
 the full size; therefore,  what we call metamorpho-
 sis, progress, development, in one sense, is entire-
 ly different from that which  we  call  by the same
 name in another case.  In  the succession of the
 changes of an individual, we have really a progress
 in one thing; but  we have in the other case a pro-
 gress  of the plan—and a progress on a plan arising
 in a succession of species which do not descend
from eacli other—which have never been derived
 from each other, as two different individuals of one
 and the same species are derived from each other
 through  successive generations.
   Therefore we should never  mistake these two
 things.  In the one case we  have  individual  sue
cessions of  changes—in the  other case we have a
plan which is successively modified and where the
progress is introduced by a series of species under-
going changes  independent from each other . and
in that view, in such a progress, such a grad*tion
only, in the plan, we recognize the mode in which
this succession so introduced proceeds in different
epochs.
  I make these  observations in reference to some
remarks made and questions which agree with cer-
tain philosophical views entertained ia some quar-
ters.  Now, I have not to  teach Natural Philoso-
phy, but to give a sketch of Natural History—of the
Animal Kingdom; but as a  knowledge of the Ani-
mal Kingdom has  constantly a bearing on philo-
sophical questions, of course you cannot avoid ref-
erence to them.  But I would only make this dis-
tinction, that  in the case of the metamorphoses of
individuals  we have a series of phenomena arising
from the fact, that the species has been called into
existence with the properties of undergoing suc-
cessively these  changes.  But with  the progress
of species,  as we find them  in different  geological
strata, the question is:  can we find in Nature ex-
ternal causes which will produce these changes?
and, again, can we refer these successive appear-
ances of different types to the influences of external
causes?  I say no; because, since Man has studied
Nature he has never seen any species modified un-
der external  influences.  The most ancient monu-
ment whose  mummies have been studied,  shows
animals quite identical with those who live in the
same country now; therefore we see, that as far as
we can reach, the  species  which exist  now have
had the same characteristics  which  they have  at
this present day ; and, therefore, it would be illogi-
cal to suppose that what does not occur for so long
an amount of time has been the cause of all the va-
rieties which we see in Nature.  And  again, the
fact to which I alluded in the last Lecture, that such
a vast variety of animals, living in the same cir-
cumstances, in tbje same locality, and again animals
of the very same types as we have in the different
geological  epochs, shows evidently that these ex-
ternalcircumstances are not the product—have not
been made by external influences—but have been
arranged with  the plan which was formed at the
beginning,  when the world and the organic beings
were called into existence with the end of introdu-
cing Man.  (Applause.)
  These views—to which I shall recur when I come
to speak of the position of Man in Nature, and of
his relations to the Animal Kingdom—disagree en-
tirely with the views, and have not the slightest
alliance with the views of  a  work which is very
much spoken of, but which I consider entirely un-
worthy of notice by any serious sceientific man—be-
cause it  is made up of old-fashioned  views which
have been  brought before the notice of the public  for
half acentury.by the French school, and are support-
ed only by antiquated assertions, and by no means
by facts scientifically ascertained. It must be owing
to some particular circumstance that this work has
been so much noticed, because really it is not wor-
thy a critical examination  by a serious scientific
man.
   Now,  after this too tedious explanation, let  me
come back to my proper subject, and I beg to  be
allowed  to go  on  regularly with the subject, as
questions are frequently submitted in reference to
Lectures already delivered, which really are not rel-
 evant or pertinent to  the present object of our in-
 vestigations.   In the  proper place 1 should have
 been led to speak of the  points which have been
 the  subject of this  explanation, and tbe remarks
just now  made would with  more propriety have
 been introduced at  the close of the Course, had I
 not been asked so often to give my views in rela
 tion to these questions. (Applause.) 
26
Prof  Agassiz's Lectures.
   I  remarked that the gasteropoda are not prop-
 erly classified.  Their structure is generally well
 known, but the details of the different groups have
 not been sufficiently ascertained for  the purposes
 of a strictly natural classification.  The gills, which
 have been made the principle of classification, vary
 so much, and the variations are of so  little impor-
 tance that I do  not suppose a natural classification
                         can be educed on that
                         principle.   You remem-
                         ber  I  mentioned  the
                         Phlebentera as the first
                         group.  The alimentary
                         canal is  distributed in
                         chem in a manner similar
                         "o blood-vessels, and dif-
                         fuses the product of di-
                         gestion   through   the
body, and even in the gills.  You have here this canal,
which is a ramification  of the alimentary tube, and
vou see here how a vessel, as it were, runs in the
branchi, which is nothing more  than a duct arising
from the  alimentary canal, and performs functions
similar to a blood-vessel.
  The next group  is the Trochoids, according  to
Cuvier.   This group contains the only species pro-
vided with shells.  There is a circular opening  in
the shell, without the notch, and the animal is quite
similar to those  which have  a notch; and again,
quite similar also to some of the naked  animals. To
those familiar with the structure of Mollusca it will
be obvious that there is scarcely any difference be-
tween this  group and several of the other classes.
The only difference appears to be that a portion of
the animal is in one case covered with  shell, and in
the other it is naked.  I am satisfied, then, that the
distinction is not natural, but that this group should
contain  all  the naked  mollusca, which  have the
same structure.   The difference between those
which have and those  which have* not the notch is
of no value at all.   I will quote an example: The
common limpet has no notch, but there is an open-
ing on the side, for the introduction of the water, as
large as on any of those which have a  notch, and
the animal can breathe without coming  out of its
shell just as well as  those which have  this long
membraneous  tube coming out of their notch.  It
forms a group  entirely different  from  all  these.
The classification  of the gasteropoda, then, is not
at all natural. Perhaps this may offer an inducement
to some young naturalist to begin the study of this
class of animals, which are so numerous along these
shores, and some types of them so large that an op-
portunity is afforded for their examination such as
is not to be met with on any of the European coasts.
  I have yet to speak of two additional  groups of
the  gasteropoda;  and first of the Pulmonata, or
those provided with so-called lungs.   The  slugs—
the snails,  belong  to  that group.  They form un-
doubtedly a natural group.  Though they have an
organ of breathing  similar to the gills of the other
Mollusca, it is peculiar in this respect that the air
which is brought in contact with the blood vessel is
not mixed up with water.  These animals breathe
the atmospheric air and not the small quantity  of
air contained in all water.  They  are  well-known
under the name of land and fresh-water shells.
                          I would here mention
                       la peculiarity in the respi-
                       ratory structure of these
                       [animals which is worthy
                         if notice.    In this pro-
                       jective  portion  of the
                        ■ihell  we have a  large
                         avity opening  outside
                         if an oblong hole.  The
                        I >vhole of this cavity  is
 covered with blood-vessels, parallel to each other bat
 connected by transverse vessels, and forming a kind
 of net work all over the cavity, so that the air which
 is introduced into this cavity at  once is brought in
 contact with  a great  many  blood-vessels.  The
 heart is near the base of this cavity, so that from
 there the blood is carried directly to the respi-
 ratory organs.   The only difference, then, between
 this organ and the gills of the common Mollusca is
 that the blood-vessels are united  with the vessels
 of the cavity,  and do not form a tube-like free ap-
 pendage hanging in the water.
   The number of  species in this group  is very
 considerable.   There  are  as  many living in the
 fresh water as there  are upon the dryland; but
 usually they seek moist corners when they  conceal
 themselves, along fences, or  between the  roots of
 trees in wet localities.  They are very  voracious
 and consume a great  quantity of carrion,  and are
 thus useful in many respects, though in otherrespectg
 they are  quite the reverse, being often very de-
 structive in our gardens.
  Another group  is that of the  Terrepadte, not
 mentioned in my diagram, because I consider the
 classification as little natural as the others.  It has,
 indeed, been shown by a Russian naturalist that
 they  have such an affinity with  so many other
 groups that they  should  be divided and  placed
 among the different families.   What was consider-
 ed the common characteristic  was a kind of mem-
 braneous appendage on the sides of the head by
 which they swim; but this is not formed in all by
 the samepart.  In some it is a dilatation of the body,
 in others  of the anterior  ridge of the head; and
 therefore you see in this case a classification of an-
 imals in  one group from an  external  likeness in
one respect, which is not owing to an uniformity of
 structure.

                     I now pass on to the  exami-
                    ationof the Cephalopoda. The
                   diagrams present numerous il-
                   lustrations of this class.  Here
                   are some without an external
                   shell.  Here is one apparently
                   naked, which  has an internal
                   shell.  The most striking exter-
                   nal feature is that the head, is
                   mire distinct than in any other
                   nollusca.  There is  a contrac
                    ion  about tbe anterior ridge
 wnere we see two distinct eyes. The  posterior part
of the body is in the form of a sac. Around the head
we have membraneous appendages which have
been called arms or feet, and on whose surface you
 see numerous snckers, by which these animals seize
their prey and convey it to theirmouth, which is in
 the centre of the tentacles.  Some of the cephalopo-
 da have only eight of these tentacles and feet.
  Here you have eight of the same size ;  and two
 much larger, of different form, with a cylindrical
 base and flat extremity.  Some are even provided
 with hooks in this more elongated form, by which
 they seize their prey more vigorously.   In this
 species the arms are very numerous and they have
 appendages like   numerous  tentacles,  forming
 bunches, which are arranged around the mouth in a
 similar manner  as  the  four tentacles in  the other
 species.
  In  their internal organization they agree  in this
 respect—all are provided with  large gills placed on
 the sides of the animal; and at the base of these
 gills we see two venous hearts and one which is
 colored in blue  and another in red.   80 that there
 are three hearts in these animals.   But when we
 here speak of several hearts we must understand
 what we  mean.  These several hearts  are  little
 
The  Animal  Kingdom.
27
more than dilatations of the tubes which carry the
blood.  They are large sinuses in the blood-vessels
and not muscular hearts  like the  hearts' of higher
animals.  The  blood reaches the heart from the
two  large-lobed sacs situated  at the base of the
gills, which are considered as hearts by some nat-
uralists.  They force the blood into the gills, where
it is brought in contact with the extensive surface
of water, and then it is changed into arterial blood
and  is again appropriated for the functions of blood
in the living  animal.  It then comes again into
the heart proper, which propels it into all parts of
the body.
   In the  diagrams  the blood-vessels are colored as
in the higher animals.  But it is not so in Nature. In
these  animals  the blood is transparent; and it is
only for  the sake of illustration that the coloring has
been here  employed.
   Near the stomach, between that organ and the
liver, these animals have a little gland which se-
cretes a dark-colored fluid of a very  dense  consis-
tence, which is used  in  the manufacture  of the
" China  ink."  All the cephalopoda have their sac
filled with  this black or rather brown substance
in great  abundance, and it is so tenacious that in all
the  fossil  cephalopoda, which are very numerous,
those ink-bags have  been found in the fossil state,
full of fossil ink—and this fossil  ink is so well pre-
served that when  prepared it has been used in the
same manner as the China ink made from  the  re-
cent cuttle-fish.   I  have repeatedly seen fossils
drawn with the China  ink furnished by these shells
existing for thousands and thousands of years in the
strata in which the  greatest number of these ani-
mals is found.
   I have just mentioned that in this group we have
some  without a shell, some with an  internal shell,
and  some with  an external shell.  This clearly
■hows how little  value can be placed in the exis-
tence and possession of shells, and how erroneous
would be  classification resting only  on that prin-
ciple.
   In the form  of  the  shell this  group presents a
marked  difference from the  gasteropoda.  In both
types the shell is  rolled up, but  in the gasteropoda
the  animal moves sideways when roliing  up, and
thus in the snail you have the right hand side turn-
ing  on the left hand side.  I will illustrate this by
a diagrams:
tances, constantly growing as the animal grows
larger; and the animal occupies only the anterior
portion  of  tbe shell, though it formerly occupied
all these  partitions,  only  when growing larger it
moved on and formed partitions between itself and
all these chambers.
  The siphon which communicates with the heart
is in part a prolongation of the pericardium.  We
have  only  one genus of these chambered  shells
rolled up in that manner  living now, and another
where the  shell is not entirely rolled up as it is
here, but where the successive convolutions are
detached from  each other, so that it is as you see
here:
  In the cephalopoda the shell is rolled up in avery
 different manner.   You see hero the back  outside
 and the  lower reeion below and the right  and left
                    'mud side are symmetrical.  So
                    hat the  cephalopoda  which
                   |rolls up to form its shell, rolls
                   |up head forward and back out-
                    -He,  while  tbe  gasteropoda
                   |iolls in a different manner.—
                    Av'uin, in the gasteropoda the
                      ciiur of the shell is  com-
                   ||)lrhly occupied by the aui-
                    iuhI when it is contracted.—
                    ^ot so in the cephalopoda, or
                    it. least in most of them. There
                   ' ia one which makes an  excep-
tion.  Tha nautilus proper is divided into numerous
chambers, and those chambers are  at  equal dis-
  This has been called Spinrfa. It is an animal not
very well known.  Though found on these shores,
it is rarely met with in a good condition for exami-
nation.  The siphon passes through all these parti-
tions in  a similar way as  in  the  nautilus.  These
two are the  only ones now living with chambered
shells ; and you will perceive that it is this animal
which has not simple tentacles, but bunches of ap-
pendages forming masses similar to the tentacles
in other diagrams.  The structnre  of the gills and
tentacles alone considered would make the nautilus
inferior to those beautiful  animals in our seas.
  There are  other anatomical reasons to consider
the spirula as  well as the nautilus lower in their
organization than the true  cuttle fish.  The fact
that they are  rolled  up in this manner, while the
body is  straight in .hese and comes nearer the nat-
ural symmetry of an animal  having  a longitudinal
diameter and  two symmetrical sides, shows evi-
dently that their type is higher than that.
  Now all the cephalopoda found in a fossil state
below the coal, during the coal epoch—during the
series of sec mdary rocks—belong to this group.
They are as numerous as  the gasteropodaare in our
seas. In a living state we  have  only two types,
but hundreds and thousands  of them are  found in
all the ancient strata, up to the most recent depos-
its forming the outermost beds of  the crust of the
earth. Those which have internal shells have also
existed in former epochs, but not very late.  They
are only found in the oolitic  beds,  in the  series of
strata extremely extensive  in the British Islands
and  Continent of Europe, but found in a very rudi-
mentary condition in this part of the world.  They
are well known in every  part of Europe under the
name of "devil's  fingers."  They have a conical
lorm, and yiside of them  a hollow cone ;  and this
cone is divided into partitions, and on one side it is
prolonged in tbe form of a flat disc.
For a longtime it was not li-iowu to what grjup 
28
of the cephalopoda  they belonged.   Tbey have
been  considered  as  belonging  to the chambered
shells in the division of this hollow  cone.   But
when studying the shell which is found in the back
of the cuttle-fish, and is known  under tbe name ol
"cuttle-fish bone," I found that this disc is divided
in the interior by plates of calcareous matter.
  But it had not been noticed that there was con-
stantly a little point here, which,  when minutely
examined, is found to be  hollow.  On  comparing
the arrangements of these plates it will be found
that they go into this point, and  in fact the cuttle-
fish is a belemnite in a reversed  position.  So that
there is  no doubt now—and this explanation is
generally admitted—that the belemnites are  by no
means the external shells of cephalopoda, but the
bones of some cuttle-fish of the oolitic series;
and the fact that in the beds where belemnites oc-
cur, we find the  greatest quantity  of  those loose
ink-bags in a fossii state, is  a confirmation of that
view.  (Applause.)
  The naked cuttle-fish of our day are numerous  ;
and as you see, have  tentacles  arranged in pairs.
Those which have only eight tentacles never have
a hard shell or any hard part.  Those, on the other
hand, which have ten tentacles  always have hard
parts.  But in some of them this  shield which is
placed in tbe back is cartilaginous—not very hard
in the species common here, but in the common
cuttle-fish of Europe, very hard and calcareous.
  Now, it is not enough to have shown that  the
chambered class  are  last and  appear first—that
those which have an external  shell are younger,
and follow those which have bard plates.  I want
to show that there is a very regular mode of sue
cession in these.   In the most ancient  beds  below
the coal where the chambered shells are the most
numerous, we find types already  with varied plates.
I have shown already how these chambered  shells
are rolled up.  It is not necessary then to draw a
Prof. Agassiz's  Lectures.
full shell, but just enough to give a notion of it.
  In the most ancient strata some of these chan..
bered shells are perfectly straight, having a siphon
in the centre, or on the margin of some of them.
  Already  these two types  occur in the  mos
ancient strata, and you see here the beginning of a
series which will pass through  all possible modifi-
cations of their shape.  Some have the shell curved
only in  this  way  with a partial  curve, and
some have the  shell curved thus,  like a hook ia
the beginning, and then becoming quite straight:
  Here are specimens of these extremely diversi-
fied convolutions •
  All forms of convolution, as it were,of the straight tube  are to be found in these  shells just at the
epoch when tbe family dies out 
The  Animal  Kingdom.
29
LECTURE  VII.
..Peculiarities of their Nervous System.
DTscovery of Mr- Blan-
           .How do
Animals....Results of Recent  Investigation..
eles....General Structure of the Articulata....r owi-i'"=. "'n."ur*u»T~;«»"i,"=.~nV"inV»«fin»l Worms....
chard....Worms....Great Variety of Form and Structure....The  He»»^" ^^^"^tow DUcoverles
the, comVo Exist in other AnimJ.?....History of^he »o™^n.SLI05:SaphS?-non of Red Snow.
___The Theory of Spontaneous Generation Exploded.
                                                                        When he divided the
        CLASSIFICATION OF THE ARTICULATA.
  1.. Vssmf.s................(Worms.)
      1. Helninthti.......(Intestinal Worms.)
      2. Apoda............(Withfeet.)
      S. Cketopodm........(With feet like hairs.)
      A. DortxbrmckuUa ..(Gills on the back.)
      5. Tu»u(iir«ncAu>ra.(Gills like tubes.)
 U. .Ihsecta................(Insects.)
      1. Araoknoid*.......(Spiders)
      2. SucUrim..........(Suckers.)
      3. Mandiiulmta.....(With jaws.)
Ill. .Crui tasea............(Crustaceans.)
      1. Puratita..........(Parasites.)
      2. Eritomostroc*.....(With articulated  claws.)
      S. ilalacottrocu.....(With calcareous claws.)
  Ladihs and Grktlemer :—The subject of the
Lecture this  evening will be the structure of the
Articulated animals in general and of the worms in
particular.
  The general structure of this order of animals is
well known.  The bodies of these animals are per-
fectly symmetrical.   The two sides  are equal.—
We have no  longer here any such differences be-
tween the right and  left hand sides as we  have
among the Mollusca, or anything similar  to tbe ra-
diated structure of the lowest type of the Animal
Kingdom. The Crustacea only show in their limbs—
in their claws—such a difference.  In  them we see
frequently one of the claws  much longer than the
•ther.
  But it  is well  known  to  what circumstances
this difference is owing.  The Crustacea frequently
lose the claws and these limbs are  reproduced, but
usually of diminished size.   When the animal does
■ot meet with such an accident, the claws continue
of the same size, and this accidental disparity is
still farther illustrated by the fact that sometimes it
is the left and sometimes  the right claw which is
smaller than the other.  This shows that  tbe differ-
ence in size is not a characteristic of the  type.
  I propose  to divide the Articulated animals into
•nly three classes—the Worms, the Insects, and the
Crustacea.
  This type has always heretofore been divided into
a great  number of classes, and even some classes
have been left out of  the Articulata,  which I think
really belong to that division, and here, in this con-
nection, I design to make a few critical remarks
on the general classification of animals as we find
them in the most recent works on Natural History.
This classification  has not kept pace with the  pro-
gress of our knowledge.    Our  text-books do not
jive the results of recent  investigation and discov-
ery.  I  would refer  to the best of the  classifica-
tions, not perhaps the most recent, but the most
extensive—that  contained  in  the  great  work
of  Cuvier  on  tbe  Animal  Kingdom.   That
is the greatest work on  Natural  History; not
very  volaminous, in five octavo  volumes, in which
the celebrated author has given the  general char-
acteristics of  all the principal types of the Animal
Kingdom, and for the  first time classified them  ac-
cording to their organization. It was Cuvier who
for the first time divided the Animal Kingdom into
four  types—who  recognized four different modes
of arrangement in the  structure of animals, and
that there was not  a simple gradation from the low-
  armation oi lotesunai  »»""«"•••   ?A a
  .Explanation of the Phenomenon of Red

er to the highest animals.
Animal Kingdom  into those four groups, he desig-
nated those groups by a  very happy name lor
which I cannot find an English term sufficiently ex-
plicit.  He  called these divisions embranchments.
By this he conveyed the idea in a felicitous man-
ner that  the groups of the Animal Kingdom  did
jeitherform a single series nor parallel lines, but a
jomplicated grouping of individuals connected to-
;ether by affinities in a similar way as the, branches
of a tree, forming groups with very natural propor-
tions, though not divisible  into families of equal
value.   Tbe groups we may call types—great di-
visions of the Animal Kingdom.  For want of a bet-
ter name, some have proposed the term " depart-
ments."  Thus you see, if lam correct, that we
have not in the English language any  terra which
conveys  the idea so happily as that employed by
Cuvier.                                   . .
  When Cuvier divided the Animal Kingdom into
these four groups, some of the groups had not yet
been  studied  anatomically as  fully as they since
have been studied, and therefore it is not to be
wondered at that that illustrious  naturalist intro-
duced into several of these groups animals which
did not properly belong to them—that have only an
external likeness—which  are analogous to them,
but not really  identical in their structure.  For in-
stance, in the  group of Radiata to which I  refer
only  three classes—the polyps, the acephala, and
the echinodermata,—Cuvier had five classes, one
of tfrem being the  class of intestinal worms—
the   Hdminthes—nni  the   Infusoria, a  class
which, I  think, must be entirely  broken up,  and
does not form  a natural  group, but contains  ani-
mals of very different  structure, and  which have
been combined together as a class only in conse-
quence of  their minute size.  That  is the only
characteristic  which they  have in common, but
their structure is not such as to justify this union in
one class, nor to justify their admission as a natural
group among the Radiata.
  Cuvier, Lamarc and other eminent naturalists
were induced to maintain the class of Infusoria,  in
eonsequence of the general arrangement of vibra-
tory cilia around the mouth, presenting the form of
a circular disc vibrating round the mouth, and giv-
ing these animals an appearance of radiated struc-
ture like some of  the  polypi.  But on examining
the bodies of these animals, it has been found that
there are transverse  divisions in  these  animals.
Borne of  the infusoria have been found to agree  so
fully with  articulated animals that  nobody now
doubts the  propriety of combining at  least the so-
called Rotifera with the crustaceous animals.  Oth-
ers are worm-like,  and belong more properly to the
Vermes  than any other group, and we know that
many of the so-called infusoria are merely germs of
plants which have been mistaken for animals; and
germs  of different other animals which have been
mistakenfor full-grown animals. Thus it has been
iiscovered recently that organizations which have
been regarded as independent animals, and as such
bave been placed among  the infusoria, are really
the young of certain Mollusca—certain gasteropo-
dous mollusca.
  Now such mistakes should be corrected.  When 
Prof.   Agassiz's  Lectures.
30
they were made, the facts by which we are enabled
to correct  them  were  not known.  The works in
which the mistakes  occur are and must long con-
tinue to be the great fundamental books of Natural
History, and hence the greater necessity for rectify-
ing these errors.
  The class of intestinal worms, heretofore ranked
with the Radiata, belongs  to the Articulata.  All
these worms are articulated transversely.  These
articulations are very  numerous.  But tbey have
a circle of radiated folds around the mouth.  Hence
the mistake to which I  have alluded in classifying
them with the Radiata. The existence of a nervous
system with ganglia was then unknown—so that
the mistake of Cuvier cannot  appear strange, par-
ticularly when we reflect on the extreme difficulty
of observing the structure of many of tbe intestinal
worms.
  1 have said that I divided the Articulata into on-
ly three classes, though I admit all the intestinal
worms and the greater number of the  infusoria.
Cuvier admitted more classes  than I  think proper
to admit.  The spiders were considered by him
as a class  distinct from the  common  insect, be-
cause they have no wings and  because their respir-
atory organs are somewhat different from those of
common insects. But many  true insects have no
wings;  and  when tracing all the modifications of
certain insects we find the transitions so gradual as
not to allow the differences between them to be of
the value which was formerly placed upon them ;
and so the class of spiders is  now merged in the
general group of insects.   Beside, we have now
ascertained that the metamorphoses of insects are
not so peculiarly a trait of that class as was for-
merly  supposed, and therefore  in the absence of
that characteristic in the spider we do not see the
same ground of making a prominent distinction be-
tween them and insects.  There  are many insects
which do not undergo so striking  a metamorphosis
as  the butterfly   and  some  other  two-winged
insects.                                 •
  Then again, certain Crustacea,  which bad been
distinguished as a particular class,  must now be
combined with the true Crustacea. It will perhaps
appear  singular that the Balani—there is a com-
mon English term for  them,  which now escapes
me—ah! I recollect it, the "barnacles"—shonld be-
long to the Articulata.   They have been  placed
among the shells.   But that classification was erro-
neous, and this is perhaps one of the most unex-
pected  results of  recent investigations.   Even
during the lifetime of Cuvier—til teen years ago—
nobody suspected that the barnacles did not really
belong to the class of shells.  Cuvier himself pub-
lished an elaborate  paper on  the  nervons  system
of the barnacles, in his memoir on tbe Structure of
Mollusca, and he considered all  barnacles as true
mollusca  He made only one remark, that  be was
struck by the complicated nervous system of these
animals; and that remark has been the foundation
of that true distinction between the Mollusca and
Articulata.  He found that tbe ganglia were more
numerous in barnacles than  iu  Mollusca, where
there is only a large ganglion  above, and another or
two below the alimentary canal; while in the bar-
nacles we find that below the  alimentary  canal
there are several ganglia, and when comparing the
nervous system of the  barnacles  with that of the
greater number of Mollusca,  and  with that of the
rreater number of  other articulated animals, it was
found that this very great peculiarity constituted
the most striking difference between tbem.  From
that time it was suspected  that, t boo eh the barna-
cles were supplied with shells, tbey might yet be
long to the articulated animals.  A British natural-
ist—Mr. Thompson of-Cork—when engaged in the
 study of the barnacles found that the young, when
 escaping f om the egg, is a true crustaceous ani-
 mal;  precisely like other crustaceous animals, and
 fixing itself only  after a certain time, when the
 shells are formed to protect it, and combine in such
 a manner with the animal as to give it an external
 resemblance to  the Mollusca.   But tbe internal
 structure is entirely different.  So there is no doubt
 that the barnacles, cons dered as a class of Mollus-
 ca by Cuvier, do not only not form a class by them-
 selves but are true Crustacea.   This change in the
 classification is made necessary by those recestre-
 searches into the structure of the nervous system
 of barnacles and into the growth and metamorpho-
 sis of the  young.   But it has not yet been effected
 in general works.
  Through the kindness of Professor Watts, I am
 enabled to show this beautiful preparation, illus-
 trative of the structure of the articulated animals.
 This is a large Scolopendra where the  divisions of
 the body  into  transverse sections, and movable
 rings, with appendages on each side in the form of
 feet, are seen much more distinctly than they could
 be perceived in any insect.
                    The body is  divided  trans-
                   versely.   Every one of these
                   livisions forms a protecting ring
                   i>f horny substance.  Here we
                   liave  no calcareous substance,
                   inly in some lobsters. In some
                   if the Crustacea the shield  is
                   uard and contains limestone.—
 Ancso lilies ure uuited together by a membrane.
  Here is the articula-
tion, but the ring doet J
not pass  across the.
whole. There is a folcil
and the next ring isto
The membrane here it
thinner and aliows t
fold to be  formed, anr
so  the next ring  is
movable on this one.   Many of the articulated ani-
mals have  all their rings uniform and very numerous-
rfo it is with worms.  Others have  appendages to
these rings  of very varied form.   In some these
appendages  are even very complicated.  In some
insects with rinps there are as many feet as rings.
                           All the rings have feet.
                         The number of them may
                         "■each hundreds,even sev-
                          ral thousands.    When
                         ^here   are  appendages
                         '.hey are soft, as indeed in
                         general the covering of
                         he worm is  soft. The
 rin^s  are also soft, so that the body of these animals
 has a less constant form thai other articulated ani-
 mals.
  In insects, if several rings are  combined,  we
 usually  see  the  body divided into two or three
 regions—two more distinctly—sometimes three.
  You see here a long tail-
 like appendage.   Heretht
 tail is shorter—the hear
 very  distinct.  All theet
 appendages can  be com
 bined together, and we finr
 them to be very analogous
 It is in tbe worms that w<
 can best understand wha>
 they  are,  and I shall defei
 these details till I come to |
 speak of tbe worms.
   You will recollec  the characte ri6tics
 
The Animal  Kingdom.
31
ji'ler these as arising
 radiated animals.  Bear  in  mind  now that I di-
 rect your attention to the structure of the intes-
 tinal worms, which are now classed not with the
 radio»-pd. hnt tbf artir-nlqt-ed animals.
                             It is only  recently
                            hat a  yoang French
                            laturalist  found  that
                            .^lere was a nervous
                           Uystem in all intesti
                           I lal worms, evea where
                            east expected,  and
                             mnd that it  differed
 some what iu arrangement trom the common articu-
 lated  animals.  It is in this respect: that  these
 threads  go  from one
 ganglia to another, and,
 instead of joining as a
 common swelling, form
 two independent  se-
 ries of parallel nerves.
 But you see that  the
 difference is not very
 considerable. After all, _
 it shows how we ought tu
 from the juncture of the parallel threads,  rather
 than as one only with swellings intermediate ; and
 far from being the exception  to  the  rule,  it gives
 the true key to the understanding of this arrange-
 ment, which in fact  we  did  not know before the
 discovery of Mr. Blanchard.
   The class of worms, insects and  Crustacea  rest
 for their distinction particularly on the respiratory
 organs—the circulation and mode of respiration.
   The worms are elongated, cylindrical and com-
 posed of very numerous and rather soft rings.   The
 •kin shows superficial folds,  and these folds are
 movable on each other, not to be  compared with
 the hard rings of higher  articulated animals.   We
 find in worms the greatest variety  of structure__
 There is perhaps no class of  the Animal Kingdom
 which shows more of this variety. Many characters
 which are considered of the highest value disappear
 here  entirely.  For  instance, in  tbe intestinal
 worms we have no circulation whatever—no heart
 —no blood-vessel—no  blood even;  while in other
 worms of the same class and which cannot be  sep-
 arated from them, we  have not only blood, but
 blood of the  most ruddy color—blood-vessels very
 complicated, and not even one alone, butsometimes
 three or more pairs of hearts.  Thus the most com-
 plicated circulating apparatus and a total absence
 of blood-vessels are found in one and  tbe same class
 of animals.   More than that, some  of the worms
 have organs of respiration, gills, highly complicated
 gills, perhaps  more complicated than the gills of
 fishes, or of any of the Mollusca-  The  most com-
 plicated structure of the gills is found in some of the
 worms.  In others there are not only no gills but no
 respiratory organs at all.  I would go beyond that.
 In some we have an alimentary canal, which is sim-
 ple. There is only a mouth and an alimentary canal
 branching into the body and diffusing  the product
 of digestion like a blood-vessel through the organs
 without causing that fluid to  pass before  through
 peculiar tubes or through any organs of circulation.
 What, then, is there  in these in common?  Why
 combine  animals presenting such dissimilarity of
 structure ? This is really the  question I have to
 answer, because they have heretofore.been divided
 into distinct classes.  Worms wifh  respiratory
 organs and circulating apparatus have been united
 into one and  the same  class under the name of
 Annulat.a, and worms without these organs have
 been united in the class of intestinal worms, while
 some others which are less  known and are also
 parasitical have been formed into  a third class
under the name of Tubularia.  The  common char-
 acter of all  these insects is  to have the body o
 elongated form, with numerous articulations, the
 wings  connected in such a manner as to be mov-
 able on each other in all directions, the structure of
 the skin  being more  simple than it is in higher
 animals, not being divided into so many layers; and
 the  muscles so  combined with  the skin as not
 always easily to be  distinguished, so that the
 skin is formed of interwoven muscular fibres with
 hard horny rings moving on each other.
   Again: the nervous system is uniformly construct-
 ed ;  and there are intermediate types so numerous
 that between those very complicated worms with
 highly organized organs of circulation and respira-
 ■z on and those which have none at all we find all
 intermediate steps ; some where the circulation is
 farther developed but where  the organs of breath-
 ing ire not so highly organized, and vice versa.—
 From tbe uniformity of nervous structure and from
| the fact just mentioned with regard to the numer-
 ous intermediate steps in the cavity of respiratory
 and circulatory organs, we are justified in arriving
 at the conclusion that  all  these  animals must be
 combined in  one class.
   The Insecta in the full-grown state have no organ
 of circulation—at  least they have no heart.  But
 they breathe through a very complicated system of
 air-tubes penetrating into  the body, having numer-
 ous  external  outlets,  penetrating, like  vessels,
 throughout the body, and  undergoing considerable
 and very striking metamorphoses ; while/the Crus-
 tacea have a  circulation and breathe through the
 gills.  This evening 1 must, however, limit myself
 to the investigation of the worms.
   So many changes have to be made in the classi-
 fication of these  animals,  that, at present,  it is
 scarcely possible to admit any of the classifications
 in the  books; though these classifications appear
 very simple,  and are founded upon  characteristics
 very easily recognized.
   The first division of worms is the intestinal worms
 or Helminthes, which  is  their systematic name.
 They have been the subject of many speculations.
 How do they come to exist in the  bodies of other
 animals?   How can they be introduced into cavi-
 ties perfectly closed?  And if they cannot be intro-
 duced into those close cavities, how are they pro-
 duced within those cavities?   These were ques-
 tions which were apparently answered in quite a
 satisfactory manner; and  the reply—these worms
 originate where they are found. That was the com-
 mon solution of these questions; and, in fact, it has
 till recently  been believed that intestinal worms
 originated, in particular circumstances, within the
 bodies of animals, within  the alimentary  canal—
 within the  surface of the abdominal cavity of ani-
 mals in which they are found. Butisthattrue? This
 statement  rested merely on assertion; and no one
 ever made  observations  so as to prove that the ani-
 mals had been produced where they were found. It
 was only  because  it could not be  explained or
 shown how they were introduced, that it was quite
 generally admitted that intestinal worms originated
 where  they  were found.  But recent researches
 have explained the way in which these animals are
 introduced into the cavity of other animals.
  I will give the history of one  of them, and then
show what conclusions  may be  educed, and then
 pjve «nm» d«r.<»ii« of other divisions of worms.
                        The history of the intes-
                       inal worms is most inter-
                        sting, owing to the fact
                       hat they have been re-
                       garded at  affording tbe
                       uost striking example of
                       ;iontaneous generation.
                       .'In  mode  of formation
                       without  apparent cause
 
32
Prof. Agassiz's  Lectures.
has been called spontaneous  generation—the in-
testinal worms, as also infusoria, were considered
as arising spontaneously either  from a diseased
condition of the alimentary canal, or from  peculiar
circumstances, without knowing how.  Let this be
the body of a common species of fresh-water shell.
Bteenstrup,  the Swedish naturalist, disovered that
at  a nnrtienlnr  season  this  shell had worms of
                   minute size.  These  worms
                 nave this form:   Here is a kind
                  >f sucker.  Here the alimentary
                | canal, dividing into two tubes'in
                 this way—a  forked  alimentary
                 canal.   At  particular  seasons
                 these worms fix themselves upon
                 the skin  of this shell-fish and
                 within the  mucus   which sur-
                 rounds it.  They swim in innu-
                 merable quantitiesin the  water,
                 till they fix themselves upon this
mollusc; and mere they form little  cysts in which
they bury themselves.  Fixing themselves on the
•kin by means of these suckers, they  produce a
kind of irritation.  The mucus  is secreted in large
quantities and accumulates around them, forming a
kind of cell in which they are buried. They remain
there curled up in such a sac, and may be found in
great abnndance in the skin after  the mucus has
been  removed.
  During time  they are buried in  that way,  they
undergo a metamorphosis similar to that of the cat-
erpillar which is to be changed into a butterfly —
The tail is  cast, and a circle o
folds is formed around the heai
and we have then an animal o
Boch a form  which escapes froi
these  little  sacs.  The  animi
then penetrates  into the ski
with these folds, which are hun
er than the outer  portion of tr
animal.  It  bores its way int
and passes through,  the skn-
enters into tbe wall of the animal, and,  passing
across that wall, enters into the ab lominal cavity"
and reaches  the organs  contained in  the abdomi-
nal  cavity, entering even into  these organs them-
selves '

  These folds the* disappear, and  the anterior re
gion of the  animal assumes another form   Here
we see a sucker—a mouth which is  small  The in
testinal tube still retains its bifurcated form  But
here is another large sucker
foruico,  aua  with  these  two'
suckers  the animal walks over the inside of the
abdominal cavity, over the organs, in a manner sim-
ilar to the leech, and  fixes itself upon the liver,
which it penetrates, and we have there that com
mon intestinal  worm of the liver which has been
oescribed  in  the class of intestinal worms, under
«he name of Distoma hepaticum.
domiI»ial otb;er worm, are  found to enter  the ab
seensom ™?Z  m  the  sftme ™7- lh™* lately
«een someof those penetrating into the gills. One of
 the gentlemen now present, saw it within the flesh
 of the abdominal wall, penetrating through the flesh
 and  reaching the  internal organs.  It had  nearly
 gone through the whole thickness of the fish, and
 was about to reach the abdominal cavity when the
 fish was opened.  So that, in the case of the dis-
 toma, the way in which these worms penetrate into
 the cavities  of other animals is well known.  I do
 not say that all  intestinal worms are introduced in
 the same way into the  alimentary canal; those are
 not found in  tbe alimentary canal but found in the
 organs of the abdominal cavity.  We shall  see in
 what manner others are introduced into these cavi-
 ties. What is still more curious is that this distoma,
 after it has been in the cavity of the body, will lay
 eggs, and these eggs have a very singular structure

 Within the eg?, we see a young one formed which
 has this shaoe.  The  moment the shell of the egg
                  breaks the  new individual es-
                  capes, and here there are nu-
                  nerous vibratory cilia by which
                  it moves with great rapidity, in
                  i manner so similar to some of
                  the rotifera that I do not doubt
                  for a moment that many of them
                  ire only embryos of  these in-
                  estinal worms. But even with-
                  n  the  egg we see  through
                  his  shell another thing.   It
                  is very  thin and transparent.—
 When the young escapes and begins  to  move,
 that faint body inside  becomes mnw  t-rorumgrpnt
 —more   prominent—always  of j
 this shape.  At that time this-1
 free movable covering,  with  all
 fiese vibratory cilia, is cast.   L
 is no longer a portion  of ;the ani
 mal.  It is like  the skin of the I
 caterpillar which falls away, and
 out of it comes a sluggish worm.
 moving very slowly, which grows
 and grows, and we see within J
 that these extraordinary phenom
 ena which, if not observed by several experienced
 naturalists,  would be  well deemed incredible.—
 The moment the skin is cast we have a very slag-
 c-i.h  nnim^l  of this shape.   We now see eggs
                formed which become numerous
                *nd  grow.   We see some as-
                suming a peculiar form.   We
                see through this  body new indi-
                viduals formed inside, which have
                a form somewhat different from
                'hat.  When ripe to escape, their
                torm  is  like |
                •his: And now
                'hey  escape, J
                ind now they
                ,'row.    We
 have, therefore,  here a genera-
tion  arising from the egg of the |
distoma,  which  does  not  pro
duce animals of that form—a sec-
ond eenerntion.   Inside of this I
                  Tganwe see
                  ■ggsform.and'
                  hese growing so that the very
                  orm of the individual may be
                  Itstinguished, inside and when
                  •hese  new  young—the  third
                  ,'eneration---escape,  we have
                  his  animal, the common Cerca-
                  ia: the third generation from the
                  gg of the distoma.  (Applause.)
                  I have no part in these beautiful
                  discoveries.  I only relate them.
 
TJie  Animal  Kingdom.
33
(Applanse.)—Here we have animals of successive
generations  undergoing  in  each  generation  a
series of metamorphoses.  We have three alternate
generations each undergoing  metamorphoses, pro-
ducing individuals different from tbe mother, and so
for three generations, till at last we have the  form
of the common intestinal worm, which reaches the
internal cavity and there becomes  a parasite.
   How difficult to identify all the successive genera-
tions when each generation, in its metamorphoses,
assumes such different forms! But when tbe great
grandfather is reproduced in the fifth generation,
all doubt must end.
   What remains then of the theory of spontaneous
generation?   It is gone forever !  Every one now
who attempts to reason on spontaneous generation
knows that he is reasoning on what has no exist-
ence.  He is reasoning on a supposition which has
been scattered  to the winds.  (Applause)   Be-
cause one such fact well-ascertained—as that has
been, and you will see that similar facts have betn
well ascertained—is sufficient to  destroy  forever
such a theory.  Another case adduced in favor of
the  theory  of  spontaneous  generation has  been
shown to be equally  unfounded in fact.  I allude to
tl}e infusoria. But the rotifera also lay eggs.  I  have
seen some rotifera living  in the snow at the  bight
of eight and ten thousand  feet above the level of the
sea, causing the snow of higher mountains to  be as
red as blood and presenting a  most beautiful appear-
ance.  This red snow is only an accumulation of mi-
croscopic animals belonging to the class of  rotifera
among infusoria.  I have seen some of these laying
eggs.  I have had the good fortune  to have  been
able to trace some  of tbe changes in these  eggs,
not all of them,  so that I mention here an imper-
fect series of observations, because I can stand for
that; but other observers—Ehrenberg, in particular,
who has made that beautiful history; in fact created
the  natural  history  of Infusoria—have completed
the researches on this subject. Ehrenberg has seen
rotifera laying eggs  an hundred times. He has seen
the young form  and  grow within the egg.  He has
not  only seen them grow, but he  has traced  them
for a series of generations.  Individuals which he
grew from eggs he has seen  laying eggs.  He has
■een them for three,  four,  six, ten generations.  He
has even seen individuals arising lrom a stock from
which millions have  been  derived;  and now, again,
I ask,  what remains of the theory of spontaneous
generation?   (Loud applause.)
   But there are other  intestinal worms for whose
presence in other animals as parasites it is not so
easy to account.  These  are found in the  eyes ol
almost all fishes, and in other portions of the body
How they  were introduced  is a  question which
could scarcely be answered,  were it not for the
discoveries of a distinguished Professor of Natural
History in Copenhagen—Prof. Eschrich. He traced
them in fishes which were kept in a pond, so as  ;
to be able  at a moment's  notice to kill a sufficient  j
number of fishes and examine the condition of the
intestinal worms within each animal. He found that
in the scolpin of the Baltic, at  a certain epoch, there
were always very large tfflnia in  the alimentary  |
canal,  while at other seasons there were none to
be found.  He  ascertained, for a  series of years,
that the  presence of  these tenia was  periodical,
and he knew at  what season  he could  find them,
and  in what condition he  would  find tbem.—
The moment that  he ascertained  this  prelim-
inary  fact,  which cost years  of patient investi
gation, he  went on  tracing  still  farther the phe-
nomena,  till he discovered  that  these animals—
Which are exceedingly long, with   a small head, a
very slender neck and thin  body,tf extraordinary
Iprs-th, dividpd into  transverse articulations—cast,
                     atcertainsessons.the great-
                      •r portion of their body, and
                      hat he could produce it by
                      lividing this portion of the
                     'iead, the articulations divi-
                      ting  and dividing  till  a
                     .rreat number were formed.
                      When  studying the  anato-
                      nyof these links he ascer-
                      .ained  that  there was a
                      •outinuous  tube  running
                     through all—in fact, an al-
imentary  canal, but branched  in such a manner
in  every  ring  as to supply  the  ring  with sub-
stance; these branchings  of tbe alimentary canal
being  at  the same time  a sort of blood-vessels
or  organs  of circulation.   But he found, more-
over, that in each ring  there were several  hun
dreds of eggs, each having the  true character and
three essential parts of an  egg.   When these
bodies were cast, then of course innumerable quan-
tities of eges  escaped  into the water and were
swallowed by  the fishes with their food.   This af-
fords a perfectly clear solution of the  manner in
which those intestinal worms find their  way into
the bodies of these  fish.
   As to the terrestrial animals in whose cavities
intestinal worms are found, the same process takes
place.  With  the vegetables on  which they live,
there are  constantly conveyed into their alimentary
canal  innumerable quantities of eggs.  And now
we can also explain tbe reason why some animals
have one species of worms and others other species.
The alimentary canal of some has  an  influence
which the eggs of certain species cannot resist,  and
they therefore perish, while in other  animals they
grow and propegate.
   It has been still  farther  ascertained  that these
eggs exist in the blood cavity, nay, they have been
found  circulating with the  blood corpuscles of  cer-
tain animals—in the frog, for instance.
   These researches of course require great patience
and care,  as  they are attended with obvious  diffi-
culties ; but  they have  been  repeated by compe-
tent observers, and there can be no doubt of the ac-
curacy of the results.
   All this shows us how defective the old classifi-
cations must of necessity be.  Even old divisions
nf  intestinal  worms can no longer be admitted.
                   This is only one state of an  ani-
                 mal, so that it must be  combined
                 >vith that class instead of forming
                 in independent division. So with
                 others which belong to the disto-
                 ma, which,  as we have seen, un-
                 dergoes many  changes,  but is
                 'till the same animal.  Then we
                 have the Cystira which nernnng
                 ire not  rea'
w..iuj», out  only the  sacs  ii
which the  actual  worms  art
found. 'All the classifications ol
them are  vet  to be changed —
The class  Nematoideaof Cuviei
and the families Aconthocepha
la  and Frematod ea, which las-t|
contain the Distoma, must un
dt rgo an entire revolution as thi
history  of the  animal becomes

known.   In  fact, the whole  class location  ot  this
type of the Animal Kit edom should be re-written
 ai.d made to accord with  the  results of  recent in-
 vestigation and discovery.
 
34
Prof. Agassiz's  Lectures.
       i
  LECTURE VIII.
.f the. Class of Worms  ..I* Div
sions or Families-Tire Apoda, or Fre»h-water Worms
      ~Th<J  OrtKoptera....Tha Emipte
   «ViMitiei have given origin to the designs/
    , ..The Clusof Crustacea, and itssabd —

  t»dim  and Gentlemen: I  know  no greater
difficulty which a lecturer is called on to encountei
ST  ,h7t«s ted bv the necessity  of crowding a
Seat'"quanrity o?matter into a limited space  That
ST*" 3  r _.!„„.. -void on this  occasion. In tin
^^tSffatahw^trtaTe  to say on the
JroS. and introdoce the insects and crustaoea; in
Sto have some time left for the  remarks on the
hkher antoals, and for general observations on the
Kmmaof gradual or successive introduction of
SpesThrough geological times, which will, I think,
2L,itute a becoming conclusion to a course of Zo-
ological L ectures in order to show ho w.the succession
agrees with the classification and structure.
  I shall avoid repeating what I said in the last
r pcture  and proceed at once to the remaining types
of tbe class of worms.  The families  which we have
.tndipd are the lowest^-those without any external
aoDendages, provided only with transverse articu-
lations or rings.  The other  worms are  not para-
sitical • at least few them are, and most of them
have shorter bodies composed of fewer  rings than
the intestinal worms. In one of the families which
has received the name of Apoda,  and contains a
great number of fresh-water worms, we have that
extraordinary type in which the alimentary canal is
branched like  a blood-vessel.  It is a very beauti-
ful sight  to see through the transparent body, the
Btomach  branching like a blood vessel, contracting
like arteries and the alimentary fluidrunning through
tbe vessels like blood, to the periphery.  Several
are to be found in this  neighborhood  m ponds and
rivulets, some of them being very beautiful. If they
were not so minute I could have had the pleasure
of showing some of these worms,  as I have now
several alive which were  collected in the vicinity
of this City.   They are among the objects  which
will interest in the highest degree all who take the
trouble of looking for them. They are usually found
onder stones in fresh water.  Their form is that of
the leech, and they are usually mistaken for leech-
es.  The leech belongs to this type,  but is  more
highly organized than these, the so called  Planaria.
  Their form presents this appearance "~
Usually they have two eyes—but some-
times a greater number—placed exter
nally ;  and it is easy seen the eye has
not attained  in them  the  high value
which belongs to it in the  higher ani-
mals.  Here we have the opening of
the mouth, and there is  the loug  sli
mentary   canal, from  which  tubes
branch off like blood-vessels towarc
the periphery in all directions. Thest
vessels are  usually of a  darker coloi
than the  body itself.  Some have appenaagea tiky
tentacles, varying much in the general outlines, but
all have  this  general form  and are usually flat.—
They fix  themselves by this  large mouth on the
bodies en which tbey prey.  The transverse  artic-
ulations  are  scarcely distinguishable.  A flat den-
tation on the margin is all that is teen ofthem.  It
fact, it has been doubted that they belong to the
type of articulata,  and if it  were not for the struc-
ture of  the  nervous system these doubts would
If
                 Rnrlimentarv  Feet.. ..Respiratory Organs of this

                               niuials___Disappearance of tbe
                               The Class of Insects—the most
                                 studied,—Illustration  of their
                                 ings___The Order of CoUopte.
                               Aptcra___TheirStruotur.il Pe-
 >>rVter'ms Suet or i* and \Und,bulata... .The Metamorphosesof Insects
ions.  .Structure of the Eye, of particular Classes.

           have some value.   But it is owing to  the  very
           transparent nature of the tissues of the body that
           these articulations are so slightly marked.  The
                              leech belongs to this type.  It
                              las a straight alimentary tube
                              ind also large jaws armed with
                              eeth.  Some have two jaws,
                              ithers have a third,  and thus
                              .be bite makes a triangular cut
                              m  the  skin of the animal on
                              which they fasten.  The  all-
                              •nentary canal,  now and then,
                              <bows dilatations, and theiedi-
                              latations correspond to the ar-
                              ticulations of the body.  There
                              is one point in the structure of
           the iceuti wmcu must be considered; it is this: that
           the number of transverse ridges on the skin is not
           precisely in correspondence  with  the number of
           nervous  ganglia.  There  are in several species
           three or four such ridges to one  swelling.  As very
           little in a physiological point of view can be learned
           from this species, I pass them,  and proceed to the
           earth-worm.  This class begins to have feet.  But
           these feet are  exccedinglv slight  and  simple.
           we have here transvers<
           articulations, we willsei
           that some of them an
           more   prominent   thai
           others.  Three or four o
           more are more prominent,  lu every ring icicit are
           strong bristles or hairs, and these are the rudiments
           of feet—not articulated, only movable in their case,
           and it is by the motion of these stiff hairs that the
           earth-worms move  about and burrow in the soil.
             Tbe respiratory organs here are little holes on the
           side opening outside,  and with ramifications like
           blood-vessels inside.   All these  animals are ter-
           restrial, but there are a great number of worms
           provided with feet  living in the  sea, and these have
           external appendages which are  provided with little
           membraneous cells in which  blood-vessels  ramify
           and act like gills.   These worms lie buried in the
           sand and are not seen unless the sand be disturbed.
           Some swim freely on the surface of the sea.  Some
           ofthem are extremely beautiful and exhibit a great
           variety of color.  Many, however, are very uniform.
           The principal and most interesting point in their
           structure is  that their transverse rings, which are
           very distinct, are usually provided with two sorts
           of appendages.  In the upper region we have usu-
           ally blood-vessels ramified and forming  an exter-
           nal gill  extending toward the back,  and these
                             jtiff hairs  sometimes  in the
                              hape of  a  brush;  sometimes
                              tronger  and articulated even.
                             Sometimes there are two such
                              irushes of hair, one above and
                               ...  other below the  gills.  In
                           _ his respect the worms vary ex-
           cet-au.^.y, uu.. ihus the position of these stiff hairs
           p.nd of the gill is  not the seme in  two species of
           these worms.  Ow ng to these differences and to
           the physiological interest of their structure, the
           story of these worms is one of  high interest. For
 
The  Animal Kingdom.
instance, we can  see all possible transitions be-
tween such a complete gill standing  out and form-
ing paddles or  feet, and a more simple structure
which is observed in others where there is a kind
of bladder standing out  with a few blood-vessels;
and these have some hairs also standingout above
and below this vesicle.  Now when we examine in
detail all these  complications, we see here only a
little vesicle, the remnant of the largs one. which
has diminished in proportion as the blood vessels
came out  and formed a gill.  T;i-- rroup of worms
which have such gills and such *tilF I'hks as organs
of locomotion have been called JJorsibrauchiata.
  There is another group of worms still more com-
plicated.  Many of them form  a tube
of sand, by means of the sucker which
takes in particles of sand which are fixed
by the mucus secreted by their skin, and
thus a solid tube is formed.  Some more
fix together fragments of shell and form
a harder  tube  in which they  conceal
themselves on the approach of an ene-
my.   These have received the name
of Tubulibranchiata.  Sometimes they
have  hard calcareous tubes.   In other
cases the tube is membraneous; others
have tubes formed as I  have said, of aggregated
particles of sand.  The distinction between these
different classes is that the body has not gills upon
every ring, but only upon the anterior rings.
  If this were the body articulated in this way we
would have here only stiff hairs on these posterior
                 . rings; but here upon  two or
                 | three of the anterior rings are
                  very complicated dills,formed of
                  blood-vessels extensively ram-
                  I ifying ;  or as many  pairs  of
                  'such complicated gills as there
are rings, of peculiar form, behind the head; and
here the head  surrounded With appendages  of a
most extraordinary kind ;
usually very long, slendei
appendages,  proceeding
from the upper part of tin
head and forming a brusl
all  round the  head,  anr
sometimes so extensive at
to conce al nearly the whol e
of the animal.   These ap-
pendages  are singularly constructed.  It is a thin
membrane, folded in the centre, so that a transverse
section would show such a position, and when en-
tirely folded  looks like a flat ribbon. It is as it were
two ribbons  folded into one,  and when opened the
animal walks in a way similar to the motion of the
leech.
  The metamorphosis of these animals is very sin-
gular and interesting.  When young these worms
are quite uniform; all the rings have precisely the
■ame appearance, and there is a simple gill coming
out from every ring.  In fact, it is not a ring prop-
                  erly speaking.   At this period
the first nug naa six  or  eignt
eyes placed in two series on the sides of the head.
As the animal grows, the posterior gills disappear—
the  anterior  grow larger
and  they gradually disat<
pear  in  such a  manner
while the anterior becotrn
more and more complies
ted,  so that several "pair
will be formed, and in pro
portion as these posterio
gills disappear the anterioi
grow larger.  The eye  also  disappears, auu iu its
place those long tentaclesbegin to grow, and it is
with the tentacles that the animal moves and feels
its position when it has lost its sight.
  I recently made the  unexpected discovery that
these animals when young are highly phosphores-
cent. While examining one of these animals not
more than  two lines in length under the  micros-
cope, on the introduction of a drop of alcohol into the
water, I perceived that the animal  contracted  and
that light was produced.  I thus perceived distinct-
ly that these  animals  are phosphorescent.  I  had
some doubt on that point, because I bad  seen in
water some of the microscopic animals which are
phosphorescent, and  feared  that  the  light might
have been produced  by their having fixed them-
selves on the worm.  But this observation satisfied
me that these worms were the  cause of tbe phos-
phorescence—(Applause)—though, as I remarked
in a  former Lecture, there are various causes which
aid in producing the phosphorescence of the ocean.
  The class of Insects is the  most numerous of all
the classes of the  Animal Kingdom. There  are cer-
tainly between sixty and eighty thousand  species
already noticed by naturalists, and  more than forty
thousand species which have received names.  We
may then safely estimate the aggregate number of
these species at some hundreds of thousands.
  Their structure  has been extensively and closely
studied.  But to give even the briefest abstract of
what has been ascertained  regarding their struc-
ture would be a  task  extending  far beyond  the
limits of such a Course of Lectures as the present.
I must confine myself to the illustration of some of
the most striking phenomena: the metamorphoses
of these animals, and the structure of their  jaws—
the organs of grinding the food—and the structure
of the wings which exist in most ofthem.
  As a class they are characterized by the struc-
ture of their respiratory organs, which are air-tubes
opening outside at the lower portion, or rather at
the lateral portion, of the wing, and communicating
with extensive tubes branching in the interior of
the animal.
  What is most peculiar to insects, however, is the
fact that they undergo extensive changes during
the progress of their growth.   They are born in the
form of  worms, and live i« that form for a  certain
time, when,  changing their  skin, they  assume
another form, and usually terminate their lives in
the form of a winged animal. In this class we have
usually  three regions of the body,  well defined: a
head, forming the anterior portion  of the body—a
middle  region, which is called the thorax, and a
posterior region, which is called the abdomen.  On
                        the last  named  region
                        we have the wings. We
                        nave here the feet. These
                        •egions  are divided  by
                        wausveise  articulations
                        nto  numerous  rings.—
                        These rings are not al-
                        ways so distinct  as tbey
                        ■ re represented  here.—
                        I'tiese appendages,  the
                        feet, are articulated, their
 
Prof.  Agassiz's Lectures.
 36

 .rmrture is complicated,  and they usually termi-
 'a?eS, s!hookPby which they seize upon  their



 Kfbod7i. ««"%fird-«hree  for the Lad,
  Sree for the thorax, and a  number which vanes
 for the abdomen, or posterior extremity
    Tbe structure  of  tbe wings varies very much.
 Some are transparent and  have  ribs branched in
 different ways   They have a very varied appear-
 ance   These are the remnants of blood-vessels. It
 has been ascertained that these nbs are hardened
 remnants of tubes through which the circulation
 wai carried on in the  earlier
 stages  of life.   In the perfec
 animal  these tubes  becorn.
 hard, and the opening is oblit
 erated.  When the  wings an
 very hard, as in the beetle, n<
 trace of the  ribs is percept
 ible. Usually, these hard wing.'
 answer the purposes of shield-
 for the  protection of the mem
 braneous wings  underneath
 and extend over the  posterior portion oi  tne abuo-
 men.  But in many insects the two pairs of wings
 are membraneous.  Sometimes the posterior por-
 tion of the wing is softer than the anterior portion.
 These differences in the structure of the wing have
 been made the basis of the classification  of many
 entomologists
 Where there are hard wings covering membrane-
 ous wings, as in the beetle, tbe insects have been
 ealled  Coleoptera.  They are the most numerous,
 and of them the greatest  number have been de-
 scribed.  When the   external wings are straight
 and hard and the lower wings are also  straight,
                  .though not so hard, they have
                  been namedOrthoptera.  Grass-
                  | hoppers  belong to this class.
                  When oulv the base of the up-
                  | per wing is hard and the  ex-
                  [ cernal  end of it soft,  they are
                  called  Emiptera.  When  the
                  whole  wing is membraneous,
                  but when the "nerves" are ar-
                   anged so as to form a network,
                  I as in the dragon-fly. they have
been calleo Neurip'era.  When the wings can be
folded longitudinally and transvpraplv as  in hops.
they have been called Hetnip-
tera.  When only two pairs ol
wings exist, they are callei
Diptera. You seelhave scarce
ly time to mention the fnnda
mental principles of the classi
fication.   It would be  interest
ing to enter  into details abou-
the structure of these win^s
but it is not possible in  tht
limits of this course.   Anothei
group of insects has been called Apccra, 01
less."
  Other naturalists have made use of the jaws of
inspcts rb the basis of a classification.  The beetle,
                       for instance,  has  very
                        powerful jaws, by which
                       it  can cut  its food  and
                        livideit just as the car-
                        nivorous animals. These
                        nws  areas follows:  in
                        he anterior  portion  of
                        he head there is a strong
                         air of plates like a scis-
                        iors, which have been
                        called the " mandibles."
WUlg-
 The head of the insect should be viewed in profile,
 and then we have this appearance, which exhibits
 the mandibles and the mode of their articulation,
   There is  another class  which have lateral »p.
 pendages.  These palpi are the organs  by which
 the animal  swallows and appreciates its food.
   These structural  peculiarities have given origin
 to the terms Suctoria and_
 Mandibulata as  designato
 ry ot these two  classes o
 insects.   .But all the ele
 mentary works on entomol
 ogy give so fully all thesi
 details that it is not neces
 ary to enter into them mort
 at length.
   1 will only add a few re
 marks on the metamorpho
 ses  of insects,  and  show
 what evidence we have for'
 the  systematic arrangement and  appreciation of
 the value of different types of articulated animals.
 The caterpillar of insects is composed of a serieB of
 rings which are  quite uniform.   The three anteri-
 or pairs have feet of a peculiar structure, which are
 terminated by hooks, and these three pairs of books
 or feet correspond to  the  three rings which will
 form the  thorax   in the/
 perfect insect.  The sev
 enth,  eighth, ninth am
 tenth  rings  have  othe
 feet of a peculiar form like I
 suckers—membraneous feet wlncn a>c use.* us or-
 gans of locomotion—and usually the last ring has
 still a  pair turned backward.  Now the nervous
 system, alimentary tube and all the organs of respi-
 ration are perfectly uniform in all the rings.  There
 is a nervous mass in every ring, so that the struc-
 ture of such a  caterpillar is very similar to that of
 any worm.  The alimentary  tube is a simple tube
 scarcely swelling in the region  where the homy
 feet are seen, and quite uniform forthe whole length
 nf fho ho-t-   R'n in tin* perfect insect, where we
                          iave the head  well de-
                          ined,  the  thorax dis-
                          iuct  and the  posterior
                          egion divided complete-
                          y from the anterior por-
                          ion, we have the ante-
                          ior  rings of the head
                          till  the same, bat only
                          me large nervous mass
                       ~ion of thesetbree nervei;
 and then in tbe abdomen we  see again this differ-
 ence.  But when some of the rings come  together
 we have a greater approximation between them.
 Here, though combined, tbe fundamental distinction
of these swellings can still be observed.   Here we
see evidence  that such insectswith  defined and
distinct regions of the body must be considered as
superior to those which have no such divisions.
  The class  of Crustacea is the highest among ar-
ticulated animals,  and  we infer this  for the reason
that their  circulation is quite perfect^ They have
 a  heart, from which proceed large
 blood-vessels, conveying the blood
to all parts of the body.  This blood
is  returned  to the organs of respira-
tion.  In a lobster the organs of  res
 piration correspond precisely to the
thorax.  They are in common chiefly
 formed by the  junction of rings on
the back and are  above the base of
 the feet.  Now if you will remember
 what I showed you in articulated
 animals, where we have here little hairs,here*
 
The  Animal  Kingdom.
37
 branching blood vessel—here a vesicle with vessels
 ramifying in it, and if we trace the whole series of
 modifications in  the type of articulated animals
 you  will readily admit that in the Crustacea you
 have only in a higher and more complicated  or-
 ganization the blood-vessels seen in worms.
   It  is not  a useless playing with forms  to  make
 these analogies.  I will  take my example from an
 actual species. We have inthe earth-worm, simply
 stiff hairs as organs of locomotion, articulated  at the
 base.  We have in many of tbe marine worms these
 hairs  not only articulated at the base,  but also
 articulated at some distance from the base.   We
 have that,  tor instance, among the  Aphroditce.—
                      But take  some of the  in-
                      sects  and  we have  a foot
                      with  articulations and  a
                      hook at the termination—a
                      foot formed  of  numerous
                     | joints and a hook at the end.
                      We may trace all these mod-
                      fications in certain families
                      of the Crustacea.   Here we
                      have the last but one. and
                      here the last joint.  Now
                      let this projection become
 a little  more prominent and you see how little is
 wanting to  make that a claw!  Nor is this  at  all
 accidental.   All  can be referred to one and the
 same type—in fact,  that
 all  these   complicated
 structures of locomotion.
 from the heavy claw of
 the crab andlobsterdown
 to the single stiff  hair by
 which worms move, are
 only modifications of one
 and the same type of ap
 pendages. (Applause.)
  The jaws  are the samf
 as the t'pet.   Tn insects the jaws are  only modified
                        Ifeet; and if we wanted
                        proof of that we have only
                        | ro look  at  the  jaws  of
                         rustacea.  In  many  of
                        | the  Crustacea  there are
                        not  two pairs of such lat-
                        eral movable appendages
                         sin the insect, but there
                        «re  as many as six  pairs.
                       [Tiie arrangement is thus:
                        Let this be the foot  of the
cmo.  vVt; can s> e now it is divided into these  rings.
The anterior one has an ap
 pendage.  At its end wes/^g!-'g-=jiL^->.<
 find an  eye.  Then com e sVSrRlwtmmagitS^^i.
 an appendage, as we set
here—internal and externa
 antennai; and here the mouth.  Here are the man-
dibles.  Then another pair more  slender; and a
 third  pair still more slender.   Then come  three
other psi's  more  complicated.  So we have a se-
 ries of appenda.gr s from tbe tail to the anterior ex-
tremity of the head.  In the posterior extremity
they are paddles, by which the animal swims.   In
the tail they are  flat appendages ; in  the thorax
they are feet ; in  Hie head, jaws; in the anterior
extremity of the head,  nopendages by  which the
animals touch their food, and the first of these ap-
 pendages terminates in an eye, and all these differ-
 ent appendages are only modifications of one and
 the same type.  Nothing is more interesting than
 to trace these modifications through different fami-
 lies.
  Among Crustacea there are a great many which
 are  parasites and form  a group.   Tbev  attach
 themselves  to  the gil'
 skin and fins of fishes.
 In these, some  of  the|
jaws and anterior portion
of the feet unite  togeth-
 er from the two sinesI
 and form at the junction
 a large sucker,  by which
the  little animal fixes |
itself on the   fish  on
which it lives  as a par-
asite.  These appendages, these sucker-like discs,
 are formed sometimes of the jaws, and sometimes
of the anterior portion of the feet.  The metamor-
phosis of these parasites is  extremely curious.—
They are free-moving insects when young, but af-
terward become fixed, and usually grow to a mon-
strous size, and change entirely their shape, so that
they are frequently mistaken for other animals.—
Many of these parasitical crabs have been described
as peculiar genera, when they are only families
which have long remained  attached to other ani-
mals.
  The form of these animals is extremely interest-
ing,  but still extremely  obscure.  The Crustacea
proper, which remain free-moving  animals, are ex-
ceedingly numerous,  and it is difficult to classify
them.  The most common division is that of Ento-
mostroca and Malamostroca.
                        Their  eyes, like  those
                      of  insects, are exceeding-
                      ly  complicated.  Of this
                      complication   you   will
                      form  some idea from this
                      diagram.   The  surface
                      of  the  eye 'is composed
                      of  a   great   number  of
                      little  eyes  united,  and
to each of which a nervous thread  may  be  traced,
arising from a common nerve  which proceeds from
the anterior or upper swelling of the nervous sys-
tem placed inthe anterior portion of the head. The
number of these  eyes varies from hundreds  to
thousands. Some  have ten thousand eyes united
to form one single hemisphere, apparently one eye.
The mode of  vision in these  animals is difficult  to
understand, and it is owing to this arrangement that
the rays only which fall perpendicularly on that
part of the eye can reach the nervous system, be-
cause every one of these little eyes is tubular, and
has not a spheroid form as the eye of other animals
  Among the Crustacea we have a series of forms,
similar to those which we see in the metamorphoses
of insects.  We have elongated types in which all
the rings are  similar, as in the shrimps.  On the
contrary, we  have other types, in which the ante-
rior region is very much complicated, while the tail
is short and curved on the body.  This is the case
of the crabs.  The latter stand  highest, and those
with elongated tail must stand next, and so down
to those which are parasites.
 
38
Prof. Agassiz's  Lectures.
                                     LECTURE  IX.

_  „.   .     e ... v^rtPhrated Animals—Fishes—Vertebrated Animals characterized by striking Differencs«
The Structure of'His. ve  f^^rmation of their Vertebral  Column.. ..Connection of the Verttbra^.&nH
   SfeTra^rac^e  .Sor, of the Fishes according to the Position of their Fins.  ...Formation of the ScSle ""f
   Fishes   Restorations of Fishes....The Brain of Fishes possessing the same essential  parts as those of high,
   Animais...  Succession of Fishes, Keptiles, Birds and Mammalia, and in the last epoch only one type-Man, who
   stands at the head of Creation.

  Ladies and Gentlemen :  This  evening I in- | coal, at the  beginning of the creation  of animal
tend to illustrate the structure and some points in
the history of the vertebrated animals, beginning
with the class of fishes.
  The vertebrated  animals,  the  higher group ot
the Animal kingdom, are characterized, as I have
already stated  by striking differences.  Their es-
sential organs—the  nervous  system, comprising
the brain and spinal marrow; and the organs of
vegetative life, the stomach,  the alimentary canal,
the lungs, heart and blood-vessels, are contained in
two different cavities;—the former  in an  upper
or posterior cavity,  according to the position of the
animal, and the latter, the organs of vegetative life,
by which the animal lives, in the lower or  anterior
cavitv.   These two cavities are formed by bones—
a series of bones called the back-bone, having ap-
pendages curved upward and uniting on the back,
forming the cavity which contains the spinal mar-
row.  Other appendages  are turned  downward,
sometimes uniting, sometimes terminating between
the soft walls of the animal, forming a lower cavity
in which the alimentary canal, the lungs, the heart
and ether viscera are contained.
  In these three skeletons  on the wall you may
see these general traits of the vertebrata, just as
well as in any of the higher classes.  You see  that
in  these skeletons the  vertebral column  is  un-
divided in  its whole length and  not  divided
by  transverse articulations.   Few  fishes have
such an undivided vertebral column.  These belong
to a peculiar class to which I shall soon refer. Gen.
erally the  vertebrated animals have this  column
formed of divided bones moving upon each other.
In those  which have an undivided vertebral column
we have a reminiscence of the condition of things
when the animal was in the egg and the vertebral
column was merely a cartilaginous string—the so-
•alled dorsal cord, which is the foundation of the
vertebral column in the new individual when very
young within the egg;  and this vertebral column
remains soft in many fishes, and in  those  which
must be considered as the lowest.  These only in
their full-grown state preserve the character of the
embryo,   it is a peculiar condition  of things—a
most extraordinary  condition of things, which  I re-
gard as of high importance in attaining a correct
understanding of the succession and  gradation of
types in geological epochs. I had the good fortune
to  notice, when  investigating these fishes,  that
there are fashes which in  their full grown state ex
hibit, m their vertebral column, precisely the same
state of things  as existed in the fish when forming
within the egg.
  The first thing which is perceived in the
fish when the substance of the upper layer
•f the egg is condensating—becoming di-
vided into  organs-is  a series of lateral
condensations,  and  between  that there is
a continuous string, which  has  received
the name of dorsal cord.   That is the foun-
dation of the backbone or vertebral column
It u certainly cartilaginous in the embryo
and remains so in the sturgeon and in seve-
ral cartilaginous fishes; and this is, most ex-
traordmary to 8ay, thenatnral   d   jf
condition of aU fishes of ancient types   In
the ancient strata-in the strata below the
life,  when the  fishes were first introduced in the
waters, all the fishes had this peculiar condition of
the vertebral column—bony ap p endages, but no ver-
tebras—no division of the back-bone—a cartilaginous
dorsal cord remaining throughout life.
  There are very many peculiarities in the struc-
ture of fishes which deserve to be noticed, in order
to distinguish  the class  of fishes  from  the other
classes of vertebrated animals.
  It appears to be of little value, but it is one of
the most striking characteristics of  this class, that
all are perfectly horizontal—all  swim horizontally.
There is  a longitudinal diameter, running from the
head to the tail, which is  perfectly straight.  Now
you  will find  that in any of the other verte-
brated animals—in the reptiles, in the frogs and
salamanders, in the snakes—the head rises more nr
less.  Even in those which have  no legs, as the
snakes, the head rises more or less from the hori-
zontal position of the body.  Another  characteris-
tic trait of the fish is to have  no neck. The head
and trunk are continuous ; so that  the fish cannot
move its head upon the neck.  The fishes movethe
head  and the  trunk together; they form a lateral
curve more or less marked, but there is no possi-
bility of an  immediate  motion of the  trunk upon
the neck.  There is one single  exception to thii-
and it is in this fish whose skeleton you see here.
  The vertebrae of the  fish are connected in  this
manner :  Just take two i
of the vertebras,with their |
upper and lower append
ages.  The surfaces by I
which the  bones unite
here, when  cut  across
would have such  a sur-
face.  These singularsur
                faces, from which these points arise
                above and these ribs below, are
                not flat as in the Mammalia. They
                are hollow cotips formed in snch^
                ai anner,f
                and theseI
                hoi lo»
                cones are |
                 Tilled wit i
                 cartilage
                 fhese ar |__
                 ticulations uo  uoi alio* say  con-
siderable motion between the vertebrae; and kthat
is the reason why the fishes have  general metion
and cannot move one part of their body oa the next
or following portion. One type of fishes has arncu-
lations  similar to those  of  reptiles.  There u
8388 
The  Animal  Kingdom.
39
 a fish  of the  Western
 waters, found also in thr
 Northern  lakes, which
 has vertebrae with hoi
 low surfaces posteriori}
 and with hemispherical
 swellings  anteriorly  on
 the articulating surfaces.
 This fish is  only  a rem-
 nant of a numerous fam
 ily, of  which  you have
 here some representa-
 tions.   They  were very  numerous,  not in the
 oldest  strata,  but in  the  so-called  secondary
 strata of the  crust of our globe, and this living
 type, whose  structure  can be well studied, has
 that likeness to the reptiles that the articulations
 in its back-bone  are movable by a ball-and-socket
 joint.   This is a reptilian structure of the skeleton
 in  this  fish—a  form  common  in many  fishes
 at an epoch when reptiles did not yet exist.  They
 are the next step in the fishes in their succession in
 geological epochs, and that is one of the first fishes
 whose vertebral column, instead of remaining carti-
 laginous, becomes bony—osseous.   Now I had the
 good fortune to see one of that class of fishes alive
 last Spring;  and  my  first thought was to  see
 whether it moved its neck, and the  first look at it
 conveyed the impression that it did.  In this re-
 spect this  reptilian fish, with  this peculiar articu-
 lation of the vertebras, has the faculty of moving its
 neck right and left,—though the neck is not divided;
 though  there is no division, the  head can be moved
 sideways.
  Another peculiarity of fishes is found in the fins.
 Instead of legs, these animals have fins of a pecu-
 liar kind, which serve the purposes of organs of lo-
 comotion.  The organs of locomotion in birds and in
 reptiles consist  of a few joints.  There  is the shoul
 der—there is the upper arm—the fore-arm and the-
 hand. They have similar bones in the posterior ex
 tremities.  All these are  detached  from the walls
 of the animal.  In fishes we have also a shoulder,
 arm and fore arm; but the bones were detached from
 the body.ouly the hand depends sideways. The arm
 remains within the wall of the animal, and the fingers
 are numerous instead of being reduced to the num-
 ber of live, as in the case of the higher vertebrated
 animals. None of the higher vertebrated animals,
no reptile, no bird, no mammal has more  than five
fingers ; there are many which have only two. three
or four fingers; in horses there is only one: the hoof
is the nail of the single finger.  In fishes, I was a-
bout to say, instead of being reduced to  the number
of five,  the  fingers are many, and  are united into
many joints.  I just stated that the  higher aaimals
have several fingers, and 1 might go on and show
the  beautiful adaptation of thehuman hand. In an-
imals which have only four fingers,  the first which
is wanting is the thumb ; then, in the next, where
there are only three fingers,  the   little finger—
the  shortest remaining—is also wanting.  In those
▼. hich have only two lingers—which is uniformly the
case in the  ruminating animals—we have only the
middle  and annular, or fourth, finger; and there are
usually  two  rudimentary fingers backward, corres-
ponding to the first andiifth fingers, and  which even
have also rudimentary nails. Where only one finger
is left it is the medial fiuger, and that is the case in
the horse. Thus, in proportion to the fingers, we may
trace the gradation of the hand or foot in the whole
series of animals. (Applause.)   This is  nothingJbut
a common anatomical fact.             i
  But beside, the fishes have other fins. 1 will just
 mention their names. First: there is  the pectoral fin
 because placed on the chest;  then the abdominal
fin, on the abdomen—usually placed on the centre o*
that cavity, but in some we have the  abdominal
fin just below the  pectoral,  and in them it  is even
more  forward.  So it is in the cod, where the ven-
tral fins are placed under the head in front of the
pectoral cavity.  The other fins are placed verti-
 cally above and below  these  bony  appendages,
 rising from the vertebral column   According to the
 position of these fins, they have received different
 names.  The one on the back  is  called the dorsal
 fin—that below the tail, the anal fin—that at the
 termination of the tail, the caudal fin.
   These fins vary very much in their form and even
 in their number   Sometimes the dorsal, caudal and
 anal fins are united into one continuous fin, begin-
 ning at the neck and  continuing till it terminates
 in the tail.  Such is the case in the eel.  This con-
 dition of fin we  find in every embryotic fish at the
 beginning of its formation in the  egg.   All these
 have a continuous fin. As the fish grows, more or less
 dentations are to be seen, and the  fins  at length di-
 vide, as we see them in the full-grown  fish.
  But what is  most extraordinary is,  that young
 fishes have the vertebral column  not  terminating
 jn a straight line, as you  see here, with a regular bi-
 jobed medial fin.   That is only seen in full grown
 fishes. Young fishes always have
 the vertebral column terminating
 in the following  manner:  The J
 white-fish, common in Lake Su
 perior and other Northern Lakes,
 has its medial fin as deeply cmar-
 ginate as this.  We have one  in ov* ri *iss Lakes
 quite similar to  the white-fish ot these Lakes ; and,
 indeed, it cannot be readily distinguished from the
 latter, unless by those who have  made Zoology a
 very serious study.   In this fish  I had the chance
 of examining the egg,  and of tracing the succesive
 t^^:*E$l!3Z$§&XBEEMKl WMcnanges  which occur
                           rhere.   I could ob-
                           serve in the young
                           fishes the following
                            mtline:   Lines be-
                            ginning here and ex-
                           tending  so all round
                           che animal, the back-
 bone  extending so, ami  men  terminating in the
 centre, so that we have here a  regular termination
of the vertebral column.  Now when the fish grows
larger this is diminished ; the lower extremity be-
comes more prominent, and after the fish has been
hatched it  changes its  fo-rm so J
 as to present that appearance.—
This  is only that  exaggerated.
 But you will easily perceive how I
readily it may  be changed, and
 even  the vertebral  column be
come regular and only  a littltl
remnant of that  irregularity re f
main  in the  curve of the very  last  part ol  tne
column.  This  is observed not only  in this fish,
but in many other fishes—in fact among all those
bony fishes whose young have been observed within
the egg. Now we will see that that  same form of tail
is seen in these  bony fishes of ancient types.  All
 fishes in the coal and below the coal, which have a
bonv skeleton, have such a termination  of the tail,
 
40
Prof.  Agassiz's Lectures.
andit is only inthe secondary strata, in the interme-
diate epoch of a succession of animals, that we find
the tail becoming more and more regular. In one of
my drawings here there isonly a slight obliquity left.
It is a fash from the chalk.  Among the fishes of our
day we have only the sturgeon which bas this car-
tilaginous vertebral  column,  and in the tribe  of
cartilaginous fish  at  large, those whose skeleton
never becomes bony—the sharks and skates—we
have also that irregular  prolongation of the verte-
bral column.
  It is a matter of surprise even now, and of course
was more surprising  when  first  discovered, that
there should be such  a strict correspondence be-
tween the form of ancient fishes, which alone pus
sessed the waters of  former days, and the changes
which we now see going on in all the young fishes
within the  egg.  These changes correspond pre-
cisely to the order of succession of fishes in geolog-
ical epochs, so much so, that more than once I have
been able from tbis  to  establish the species  and
even the geological epoch to which fossil fish be-
long.  In this country there is a full series of stra-
ta,  containing  fossil fishes which all show in their
structure such  a position of their tail—an oblique
termination, not this  symmetry—whose era must
be between the coal and the  oolitic series.  I have
seen a beautiful series of these fishes in the collec-
tion of a scientific gentleman in this  city—the most
beautiful, indeed, that I have  ever seen.
  This correspondence of structure  between  the
egg of fishes and the growth  of the  embryo, is one
of the matters which can  be  established, perhaps,
only in a class  of animals whose structure has been
fully  ascertained.  I  could show some examples
among the  acepbala of the Mollusca, because they
have been  better studied than other types.   But
the  fact  being that there is such a strict corres-
pondence between the phenomena observed in the
growth of individuals  and tbe  succession of geolo-
gical epochs, I venture to maintain what 1 have
already asserted, that allclassifications in which we
should not find such an  agreement must be defec-
tive, and canhave been constructed only on account
of want of information. In Nature, when we have
ascertained a rule of such an extent, we  are safe in
regarding it as the general rule, because there have
been observed no such exceptions in organic life.—
(Applause.)
  I see this favorite subject of mine has  already
led me beyond the limit of time to  be devoted to
this class  of animals. I  must, therefore, abridge
what yet remains to be said of fishes, in order that
I  may be able  to go through that class in this even-
ing's Lecture.
  There is  one point in the structure of fishes to
which I must allude,  as it is important in its bear-
ing on tbe study of  fossil fishes.  I refer to  the
scales of fishes.
  Naturalists have usually classified the fishes by
their fins, uniting first the fishes which  have  a
bony skeleton  and those which have a cartilaginous
skeleton; uniting, for  instance, the skates,  sharks
and sturgeons into one order—then all fishes with a
bony or hard skeleton, in  another order; and then
subdividing these two primary groups by the posi-
tion of their fins. Cuvier adopted these primary divi-
                     ssions,   and  arranged  the
                     Irishes into two great groups
                     1 -those with only soft rays
                      n their fins,  and  those
                     |vvhich had  not only  soft
                       ays, but spines  also rising
                      is_ you  see  here—hard
                     hpines on the anterior of
                     jcbe dorsal fins and soft rays
                     'oackward.
   Linnseus adopted another mode of classification..
 He divided the fishes  according to the position of
 the  pectoral and ventral fins.  He named  "ab-
 dominals" all the fishes whose ventrals are placed
 in the  middle region of the  abdominal cavity.—
 The  next  he   called  •'thoracici,"'  those   with
 ventrals  on  the   thoracic   region.   Then he
 named  "jugulars"  those whose  ventrals are  in
 front of the pectorals, and then he had in another
 class those whose fins are  continuous, as  in
 the  eels.   But  such  a classification, though
 readily  learned, is not at all natural,  and  does
 not bring the fishes together  as they  are really
 related.   The classification followed  by Cuvier
 in  which the  hardness  or  softness  of the  rays
 of  fins is  the  principle, is  not  any  more nat-
 ural than the other, which is beneath  criticism.—
 If, instead of taking the hardness of the rays, the
 structure  itself were taken as  the basis of classifi-
 cation, it would  be much more natural.   Then we
 would have fishes which have, in the dorsal, simple
 rays in front and articulated and divided rays in
 the posterior.   When these rays are divided not
 only longitudinally,  but also  transversely, the dis-
               junction has, I think, some value.
                 ;f will show  that by referring to
                  another difference. Studying the
                  fossil fishes  I could  not satisfy
                 myself with the  classifications,
                  because they scarcely ever show-
                 ed their general form.  We find
                  too rarely  a complete fossil fish
                 [to be able  to ascertain by the
               __structure—by the form of the
 fish—to what, tamily  t belongs.  But the  scales
 were  frequently  fou d  in   an excellent state
 of  preservation;  and  when   investigating  the
 subject  I  tried  to  find  in  the  scale  some
 characters  by  which  I
 fishes, or  by which I couh
 classify them.   One  pre-
 liminary fact was then as
 certained: that those fisliw
 which had some likeness
 to the ancient fishes  haii|
 scales of  peculiar  struc-
 ture.' The structure of ><
 common scale is this : Lay
 ers are  formed successive-
 ly on each other in a man
 ner very similar to the  or 1
 mation of a shell. These scalt , are ot a horny struc-
 ture. I make now a section of this scale. Such a
                        rale is a coil of layers piled
                       up,the oldest being uniform-
                       v  below, and  is covered
                        vith  a mass of considera-
                    _ ile thickness of true enam-
 i, as haru as me names'
 enamel  of the teeth, am
 the lower portion of  thi
scale is  bony substancf
showing all the charac L^
teristic  peculiarities ol uu.,j, . ...ctuie.   ribnTwe
have two varieties  of  scales, of very  different
 structure.  Now all the fossil  fishes, without any
 exception, have such enameled scales—the lower
 layer of bony substance and the upper of enamel
 of considerable  thickness. This afforded a suffi-
 cient reason for the union of all these fishes in one'
 order, especially as they differed  so  completely
 from the common fishes.
  Recent anatomical investigations have led even
 those who at first ridiculed this mode of classifica-
 tion to adopt it themselves.  Johannes Miiller, for
 instance,  of  Berlin,  who  at first laughed at  this
 singular desquamation,  as  he was  pleased to term
could  recognize
 
The  Animal  Kingdom.
41
it, has himself acknowledged that it was the most
fortunate hit I made in Ichthyology.   (Applause.)
  Every animal is cartilaginous at the beginning.
Even those animals which have the  hardest bones
have a  cartilaginous  skeleton in the  embryotic
state. It is only at a later period of  life that they
become  bony.  That,  then, gave me the  basis for
a classification, and I think  that from that time 1
made more rapid progress than before in Ichthyol-
ogy. After  I had  ascertained these analogies I
went on, and  found that sharks always had scales
of a peculiar character, formed only of enamel with-
out bony  substance below.   All those  protuber-
ances on the skin of the skates are of enamel, but
they are not arranged in layers on a bony basis,
and.therefore, they form another type. Then among
the fishes with scales of horny substance, deposited
in layers I found that  these were two types :  one
type in  which the  scales are  simple lavers  with
regular outlines ; and another ir
which the scales had  dentatec
outlines, so that every one  hac
teeth in its posterior edge, anc
that as  the  scale  grew  larger
these dentations became more
numerous, and the surface of the__
scale became gradually rougher and  rougher.  Now
we have that in the perch.  The mere touch of that
fish discovers  this peculiarity,  while the fishes
whose surface is smooth have the scales formed in
simple layers.
  A singular coincidence is this, that fishes,  with
few exceptions, which have such dentations on the
posterior margins, are just,  those which  have the
hard bony spines on the anterior portion of the dor-
sal fin ;  and more than that, the head of the fish has
something quite characteristic.
 Here we have
a  bony pi ate
which  covert
the gill.  That
willbetheeye
We have here]
a crescent
shaped  bone
movable, and
behind  which
there are three
other    bonee
movable  npoi
it,   and  that
joins with  the  lower jaw here, also movable.
These four bones here have been called  the  oper-
culum.
   Having ascertained such a connection between
 the hard parts of the animaLI became more and more
 convinced of the value of scales ; and I then endea-
 vored to  ascertain to  what families belonged  those
 of which any scales had been found, and to'classify
 the whole of fishes according to the structure  of the
 scales.   I put in one  order all the fishes which have
 only enameled granules on the skin, and called
 them Placoids.  All those which have scales cov-
 ered with  enamel  I called  (iinv)ids.  All  those
 which had dentated, serrated scales, with hard
 bone in the backbone and serratures in  tUe  oper-
 cular bones, I classed together  as C/rnoids; and
 those which had  simple head-bones, soft rays and
 soft scales, with  simple outlines, I classed together
 and called Cycloids.
    Of course, when studying the different families,
 I found the similar relations in tbe details which
 enabled me to find correspondent  adaptations be-
 tween the higher characteristics by which we dis-
 tinguish genera and species.
    Now, I was enabled to " restore" a fish from iso-
 lated scales.  So much  has been said about that
that I will show  how  possible,  and indeed how
easy it was for any one who took the trouble first to
investigate these relations.  I have shown how the
different modifications of the structure of the head-
bones are related to the structure of the fins and the
structure  of the scales.  I will  not try your pa-
tience by  going into details, but 1 willoniy show you
how easy  it was, from the knowledge of these  re-
lations of the scales to other portions of the animal
to give the probable and approximative outline of a
fish when you have had only  a single scale as a
starting point.  (Applause.)  Let me draw a scale.
A great many fossil fishes have  angular scales of
this oblique form.  That portion  which is here en-
                ased  by enamel  is covered by a
               scale which proceeds so that I am
               allowed to draw  my outlines of
                nerely of  the enameled portions
                without drawing the portion which
               is covered.  I will make the  scale
of a  size which will enable me  to  give  the
whole thing on the board.  Let  that, then, be the
outline of the scale.  Now we  know that there are
usually forty, fifty or sixty  scales in one longitudi-
nal series from the head to the tail.  We know that
fishes which are about as thick as long have these
scales higher than tbey are long;  and  that those
 which are longer have  their scales longer than they
 are high.  These are preliminary facts easily obtain-
 ed by investigation.  We now find a scale which is
 about as long as it is high.  You see then what an
 easy task it is to draw scales of about the same form,
 perhaps forty in that line,  and you will  have to
 make a fish about as high as  it is long.  You at
 once draw your outline and  when placing your
 scales you will find  that they fit  easily,  and  you
 draw them with as much precision as if you had
 the living model before you.   But you  have now
 got a fish without fins ! The question is where are
 you to put the fins ?  And, again,  what sort of a
head are you to put to such  a  body 7  (A laugh.)
A lish which has a flat, ovate  form like that will
be a fish of not very rapid motion; and we  know
that all fishes not p issessed of powers of rapid mo
tion have  rather elongated dorsal  and anal fin*.
and that the caudal fin is not forked.   Those that
swim fast  have the tail forked, and these fins  act
as a paddle.  The fishes which have  a broad, flat
body, are notvoracious ; therefore they cannot have
a prolonged snout.  They will have a short, round
head, and  so in that way you terminate your draw-
ing. (Applause.)
  That all  that can be done with precision I had the
good fortune to be able to demonstrate in a rather
striking manner.  In the  year 1833 I delineated in
the first number of  my work on " Fossil Fishes," a
scale of a fossil fish sent me  from England, and
from it drew the fish to which I considered it to be-
long. In the following ye r, 1834, the whole remains
of the fish  were collected, and the drawing was
given in the third  number of my work.  I have the
satisfaction of saying that the two delineations do
not differ  in any essential way, even in the details
(Loud applause.)
  These restorations have been repeatedly made
They have been made in other cases where  the
process was still more difficult. Cuvier was the first 
42
Prof.  Agassiz's  Lectures.
who made these restorations from single bones of
those fossil mammalia found in the gypsum near
Paris.  He restored several  genera.  He gave not
only the whole skeleton of these animals, but even
the outlines of their forms.   Thus far he could  go,
and thus far he did go, and gave entirely satisfacto-
ry details to  his figures.  Some  imitators followed
and  went farther than  he—giving even  bair  to
these animals and  dots to their colors!  They  ac-
complished all that, but there were as many lies as
additions to the figures.   (A laugh.)
  The structure of fishes is in general the same as
that of tbe higher vertebrated animals,  except per-
haps as far as regards the organs of respiration.—
All fishes  do not  breathe by lungs as the mamma-
lia, birds and  reptiles.  They breathe  by gills, or-
gans placed in the sides of the bead under those
large covers which  protect the  sides of the head.
These gills have the fol-
lowing  structure:  Let
that be the posterior mar-
gin of the head.  Here
we have in the opercle
three, four and sometimes
more, arch-shaped bones,
usually  three  or four, to
whose  posterior margii;
we see attached  small
bony appendnges, along which blood-vessels run in
great abundance.   These are the organs of respira-
tion.  The blood comes to them immediately from
the heart, which is placed here below and has this
form.   A   large  sac receives  the blood coming
from the body, which is the auricle, and  empties
into another cavity called  the  ventricle ;  and that
empties  through  a tube which has  received the
name of aortic tube ; and here  arises  a large blood-
vessel, under the name of aorta,  which  branches
into as many branches as there are arches in the gill.
There is no continuation to this great blood-vessel.
The blood goes directly to  the gills and then comes
back after it has reached  the termination, through
 a sinus, and all these veins  unite, forming another
 large blood-vessel by their junction, which runs to
 the  back-bone and along this cavity beneath it,
 whence it is distributed to all the viscera of the ab-
 dominal cavity.  The blood,  after it has reached all
 parts of the body, returns through these veins and is
 emptied into this large sac, so that the venous blood
 comes into that cavity and is propelled into the gills,
 where it is converted into arterial blood.
  Such a circulation is called  "a simple circulation."
 But beside these organs of respiration we have in
 fishes a curious organ  placed in the upper portion
 of the abdominal cavity—a large air-sac called the
 air-bladder, which opens into the alimentary tube
 above.   This is a rudimentary lung.  It is the first
 indication of the formation of a lung in vertebrated
 animals;  and when tracing  the formation of the
 organs  within the egg we may ascertain that in its
 position and formation this air-bladder is similar*to
 the lung of higher animals.
  The  mouth opens into the gills, which form the
 arches on both sides.  The  food  passes between
 these arches, and moves on into the stomach which
 is very uniform.  The alimentary tube is scarcely
 more slender than the stomach, and is very short in
 most fishes.  There is also a large liver and gall-
 bladder, so that in the structure of the viscera the
 fishes do not materially differ from the higher  ani-
 m ils.  All of them lay eggs  in innumerable quan-
 tities.   There  are species which  lay as many as
 fifty thousand eggs.  This extraordinary fecundity
 affords a ready explanation of the great number of
 fishes, and  the non-disappearance  of  any of the
 types notwithstanding the voracity of these  ani-
 mals.                                   -^S5»«fl
  The brain in  fishes has  the same essential parts
 as that  of higher animals.  We have  also nerves
 proceeding  to  the*
 eye, the  nose ant [
 the ear, which hat|
no external outlet
but is yet quite com
 plicated. Here is an j
ether striking anal
ogy with the highe
 animals. All belom
to one and the same plan, and the order of their
structural arrangement precisely  corresponds with
their succession in  geological times.  There  was
 an epoch when there were no fishes, no reptiles, no
 mammalia.  First come the fishes, and fishes only
 exist.  Then appear the reptiles—then the birds,
 and lastly the mammalia; and in the last epoch only
 one type is introduced—Man—who  stands at  the
 head of Creation.
                                      LECTURE  X.

Geo'ogical Succession  of the  Class of Fishes....The  Vertebral Structure of FinliM p»m,h.^*w   <■ «.  •  m  .,
   The PfacoUt-Sharks and Skates-Fossil Remains of the Shark   The Ganoidl Vhlr.^\Z  of their Teeth....
   eled Scales....The genus  J^i<,0S*uS-Their Vertebral  Structure   The Allien,   °pi?l^:-^  H^Enam-
   ancient. Fisbe,-their Analogy to the Reptiles.. ..The  Ctenoid!".:  The Spare da'' "iw™ r.7  vf ^T0-8t
   Swimming-Peculiarity in their Eyes....The Herring... .The Trout    ^^00^^"   -r-V °?-.of  V»  F-sh ln
   Apparent dissimilarity in their Structure-Snakes Lizards without feet-The^            r"8 '/ ^ "L6"-
   -Structure of the Heart in Reptiles-Divi-ion of Reptiles intc^ four Ordefs •  TurflP,  i ; J i ec1Ztrd~T^eI,Fr0g
   ....Scales of the Tortoise nothing but extended Ribs ...Brain  o7Utiles  m  f '  nf^"'  ??£ket »nd Fr°g"
   the Turtle not yer,  ancient.... Crocodiles a Remnant of the Ancient" Tvplof Wds'"'Th. f ^  exl"ten«°f
   ....Fossil Remains of the Mososaurus.... Characters of AncientTyLtfete™i£ffcriAm«noan Crocodile
   .... Extensive Discoveries yet to be made on this Continent .^Lizards wtS Fp«J Comparison of the: Vertebras
   tar, Feet.  Difference in  the Structure of the Jaws in Snakes and UzaiS^Enom™. TO.tS°^e" *?& RuId,men',
   Snakes....Fossil Snakes found  in the London Clay.. ..Batrachians                 Distension of the Jaws of
  Ladies and  Gentlemen':—Through  the  kind-
ness of Prof. Watts, I have  been provided with a
series of  specimens from the  College  Museum,
which will enable me to show several facts  of in-
terest relative to the structure of Fishes and Rep-
Hies   Haying gone through the examination of the
anatomical character of fishes, we have the means
of understanding more fully the order of succession 
The  Animal  Kingdom.'
43-
 and the mode of introduction of the different types
 in geological epochs.
  I will now advert to some of the peculiarities in
 tbe families of Fishes.  I  have already stated in
 my last Lecture  that the class of fishes is divided
 into four Orders, from the  structure of the scales.
 But these peculiarities in the structure of the scales
 are not tbe only characteristics by which these Or-
 ders are distinguished.  For example: in the first
 group, the Placoids, which is covered with enam-
 eled tubercles spread over the  skin, we have a
 skeleton constantly cartilaginous.   This, though
 sometimes hard, is never  bony as in other  fishes.
 Again, the vertebra; on the central portions of the
 back-bone  are also separated from  appendages
 which stand above and below, so that the vertebral
 column can be taken out of the body like a stick.—
 Here is a specimen. You see plainly on these sur-
 faces the prominent characteristics of all fishes that
 have the whole surface articulated.  You observe
 this cavity  and, opposite to it, a similar one.  You
 see several vertebrae, one above the
other,  and  these boles form biconical
cavities.  For the sake of a clear un-l
derstanding  I will repeat what 1 have
before  explained.  Such  a portion of
the back-bone of the shark is divided
into a  series of cylinders  which are)
hollow in this manner.   These hollow
                       kcavities  in
                       (contact with each  other
                       lare filled with  cartilage.
                       ISo there are herethe hard
                       ■portions of the vertebrae,
                       land above them the ap-
                       jpendages of the vertebral
                       ■column,but separate from
                       ■the  back-bones   them-
selves, and articulated in  such a manner that they
 easily fall off.
  Another peculiarity of all cartilaginous fishes, is
to have their teeth loose, without sockets, and only
 attached to the jaw by the skin.  They are not in-
 serted in deep sockets as those of other fishes and
 higher orders of animals.   This  mode of insertion
 renders the teeth movable, so that the shark can
 erect its teeth.  The shark has  not a single row,
 but five, six or seven rows behind each other, and
 the first erect teeth are  placed thus
 On the edge of the jaw we have anl
 erect tooth, and back of it numerous
 teeth whose point is turned backward.
 As often as such a tooth is destroyed,
 the next  tooth will take its place, so
 that there is a constant supply.  The
 rows of teeth are  not always as dis-
 tinct as in this  instance.  In manyj___
 the teeth are united so as to form large  plates by
 their junction.
   In the skates the teeth are arranged in this man-
      like pavintf-stones.   This being the anterior
                         •margin of the jaw, there
                         |*re constantly newteeth
                         liorroing at the back as
                         Joften  as the  front ones
                         ■fall oft".  There are some-
                         Btimes as many as twenty
                         |or thirty in one row, all
 oT~which arn  rt nc-ved in  ilie same manner, and as
 the animal  increases in  size the series of teeth
 grow larger.  The series  of teeth are oblique, and
 as tbey fall off, those which come  to supply their
 place will fill up the whole margin of the  jaw —
 Those back teeth are formed on  a larger  scale than
 those in front.
   The order of Placoids  contains  two  families-
 sharks and [skates.  These  two families,  though
very different in form and strncture, have this in
common—their gills  are merely covered by strips
of skin.  There are as many openings as gills.  In
the common fishes there is only one opening  in the
gill and  a series of flat bones  covering the whole
cavities in which the gills  are  contained. But in
the shark there are externally five, and sometimes-
six or seven\
fissures, eachd
of which  isLg.^nj^r^.-
covered   b>
strips of skin ; ••'>, $0k ' ':'■'
In the ■Kates.&g^igftjgjj
which   an |
fiat,  the fis-*
sures open  under the heads—in  the sharks,  on
each side.
  A knowledge  of the details  in the  structure of
the shark  is  very interesting  to geologists.  The
great number of their teeth found  in a fossil state,
renders it quite necessary for the geologist to know
what differences in their structure the teeth indi-
cate.  Their skeleton, being rather soft, is not often
preserved in a fossil state, but  the teeth being ex-
ceedingly bard, are  very  common in  geological
strata.  In the tertiary strata some are foufcd ex-
ceedingly large.  In this  shark, which is  about
twelve feet in  length, the teeth are nearly an
inch  long.  Some  are  found, having  tbe  same
form, which are several inches in  hight  and as
             much in width.  In Malta,  teeth are
             found seven inches long and four and
             a half broad at the base.  One would
             suppose that the shark  from which
             it  was derived must  have  been ex-
              eedingly large.  Such is not the fact.
              "hey probably did not  exceed some
              iving ones, being about  twenty-five
             'or thirty feet  in length.   It  has been
pposed that they were  sixty or one  hundred feet
long;  but  such is  an  exaggeration,  caused by
want of a proper knowledge of the corresponding
living species.  Sharks  of the greatest size have
not the largest  teeth, but on  the contrary, those
having the smallest body have the  largest teeth,
and it is to this tribe of sharks the fossil species be-
long.  So then we have no right to  infer that the
teeth belong to an extraordinary sized species.
   The next is Ganoids, of which I have explained
the  character from ancient strata.  This drawing
represents the one which I had  the pleasure to " re-
store" from a single scale some years ago, and I
b*ere exhibit the outlines of that taken from the spe-
cimen itself.  You will observe, on comparing this
specimen with the first outline I gave, how closely it
 agrees.  They have  not only enameled scales, but
 they are rhomboidal in the   same way as  the
 Ganoids.
   You have here one of the few remnants of these
 ganoids, the gar-pike of Lake Champlain—found also
 inthe Southern rivers.  It is provided with  sharp
conical teeth,  and is  extremely voracious.  You
can find  all the peculiarities which I mentioned,
about the position  of the dorsal and anal  fins, in
the voracious fishes.   In those which have a short
body, the dorsal fin is usually on the back and is of
a larger size.  The head is  proportionably shorter
and rounder.  The scales of the gar-pike are so very
hard that it is utterly impossible to pierce them
with a  nail.  They are covered with the  hardest
enamel.  The fin likewise is  protected  on either 
44
Prof.  Agassiz's Lectures.
 edge with similar hard scales,  which prevent the
 breaking of the rays.  Only a few similar fishes
 are found.
  This  genus  Lepidosteus  is peculiar to  North
 America.  It is found  in rivers emptying into the
 Gulf of Mexico  and the St. Lawrence.  A genus is
 also foHnd  in the Nile and Senegal called the Po-
lyptcrus, which  has numerous rays on the back.—
The sturgeon is allied to this genus.  Fossil fishes,
of which a few  smooth scales are found, differ from
them by  the position of their fins and the form of
the head and teeth.
  I have alluded to the  peculiar structure of the
vertebrae in that genus where we have articulating
surfaces of the back bones, rounded on the anterior,
and  hollow on  the  posterior extremity.  I have
shown you a series  of vertebras of the back-bone
from one of these fishes.  Though it is from a large
■species, it  is so small that you will scarcely be able
to examine it at a distance. I show it to compare the
form of these vertebra? with those of other fishes—
the shark and codfish for example.   In the form of
their articulating surfaces they  resemble those of
the crocodile.
  I have here the vertebra of the'alligator.   You
see these rounded articulating surfaces.   There is
a hollow socket in  which the succeeding vertebrae
can fit, and the  manner in which the two vertebrae
move is like  a ball-and-socket joint;—precisely
the mode  of articulation in the family of the Gan-
oids.  This peculiarity is more interesting,  as these
fishes are the only vertebrated animals existing at
an epoch when  reptiles had not yet been called into
existence.  And after the reptiles  began to  exist,
those types of fishes  became so diminished that
they were almost extinct, and  at the present day
we have only a few remnants of  them—in fact only
two genera.
  It is not the place to speak of the types of  those
ancient fishes,  and  I  would only  allude to some
more pecularities of the most ancient ones, to show
that they are somewhat analogous not only to rep-
tiles, but have some othercurious analogies. These
animals, with these
curious flat  bones
on the head and be-
hind the  shoulders,'";:'',"'■'•J^Al
have in their  form* ',j*5,."<A'>',^',«*
some resemblance'?^. Vy| '>}
to tortoises, but of a-1*   '-.'.Mii.-^
small  size.  Theyi'
have also some re-'^
semblance to  cer-l
tain    Crustacea.—1 l-'^.
They  have  been ;,'£..,""
mistaken   for  theJjj^ri
former by some  and/
for the latter by oth-"
«rs.  It is only since]
1 had am opportuni-
ty of studying  mi-
nutely their  struc
tare,   and  findini
some of their types'
more fish-like in the!
structure  of their'
vertebral  column,  that I ceuld  ascertain that this
as well as that form belonged to the class of fishes.
 rhe analogy is  so striking that it is possible to sat
lsty  any one that  this type will follow that, and
 ■mL £?g a trueJfi8h> we °"»»t necessarily con-
 sider this  extraordinary form as belonging to that

 tW w first1appearanee of the class of Vertebra
 fereyn^fron?ttafire,8embknC? t0 l™** entirely d*
WWt . SES.  e- fi8helnow  in existence, as to ex-
nibit a most curious phenomenon in  Nature,  show-
■:*^S?r*5raiM
ing us how that from the beginning all types were
contemplated by the Creator, but only called into
existence gradually.
  The ordinary bony fishes  are divided, by the pe-
culiarities of their scales, into two Orders. First,
those with hard, rough scales, called the Ctenoid*,
to which the Perch belongs.  They have  not only
spines on their backs, but dentations on their scales,
and have been divided into numerous families, ac-
cording to the structure of some of the head bones.
They are not found in general works, which may
be  an  inducement  to some to  study them.  We
                          have here a preopercu
                          jlum which is dentated
                          |or serrated.  Then the
                           perculnm which ii the
                          next  lower  is usually
                          dentated and provided
                          with  spines,  and  two
                           tber bones  below the
                          iserratures.    That is
the character of the  perch  families.  Beside that.
the perch have teeth in  the upper and lower jaw,
and upon the palatal bones  inside the month, as
well as the bones of the skull. It is a most extra-
ordinary fact that the  bone which  is known by
anatomists to form the division of the nose in higher
animals, called  the vomer, rests  upon the bonea of
the skull in fishes which have no such deep cavities
in the nose.  Tbe vomer forms  part of the palate
in the perch family, and is covered with teeth.
  Another family allied to  this, the Sparoids," to
which  the  '• sheep-head" belongs, differ in having
no serratures along tbe edge of the pre operculum.
This and two other bones>
are smooth in their edges.S
but the operculum  hasjjfji
spines, the back fin  hasj-;
spines, and the scales aret
rough.   The Scienoids.f
to which the weak-fish^
belongs, has the sameS
characteristic of the  op-*i
ercular bone, and no  teeth on the palatal bones.
  One most extraordinary family belonging to this
group is the flat fishes, for it  is the only family that
is unsymmetrical in the vertebral column.  The
two sides are not equal.  The one is flat and color-
less, ^hiletbe other is  swollen and colored-  In-
stead of swimming vertically, they swim flatwise,
on one side.   They  are  distinguished by the fact
that the two  eyes are on the side that is colored.
When young, in the egg, they are symmetrical, but
when they grow larger, and even very early, one
of the eyes  turns to one side—sometimes to the
right and sometimes  te the  left. The eye turns
the moment the fish  begins  to grow.   That side
which is exposed to the action of light is the only
one colored.   Though these fishes have soft rays.
they have  radiated,  serrated scales, thereby mak
ing an exception to the general rule  that there ii
a correspondence between the hardness of the
rays and the structure  of the  scales.   The flat
fishes form an exception to the whole type of ver-
tebrated animals, in their want of symmetry. The
name of the family is Pleuronectes.
  The  fishes  with smooth  scales are  more nume-
rous than any other types, and are the type belong-
ing to onr day.   Some have had rays upon their
backs.  The  Mackerel are of this class.  In them
we find the following peculiarity:  Let this be tbe
 
The  Animal  Kingdom.
45
body: we have here hard rays in the same manner
as tbe perch.  Numerous branches  arise and even
divided  rays.  According to the rule I gave, this
fish should have smooth scales.  On the contrary
it has serrated scales, but only on some parts of the
body—tbe other portion  is covered with  smooth
scales. It is,  in fact, an intermediate type between
the herring and the ctenoids.
  The family of the herring, of trout and of codfish,
all have the same scales and soft rays.  The family
of Codfish is distinguished by having numerous di-
vided fins—sometimes  three dorsal and two anal
fins, all ofthem with soft rays and smooth scales.—
The family of Eels has the  fin continuous with the
body.
  Then we have the families of Herring and of Suck-
ers, which differ in the following manner. In the fam-
ily of herrings the body is  provided with a single
dorsal fin, and a fin rising from the pectorafs.  The
body is  serrated all  along the abdomen.  These
teeth are formed by peculiar bones which stand out
on the edge of the body.  Each of the ribs has two
          (branches uniting, and the point which
          ■stands  out is  marked  thus:  two
          (branches  meeting.  So that they have
          loot only ribs running out from the back-
          bone, but an additional pair  from the
        _|iower margin of the body.
  In tbe family of Trout we have no such cbsjacteris-
tic.  We have an additional dorsal fin without any
ray, only a soft adipose or fatty fin. In these two fami-
lies the edge of the upper jaw is formed of the max-
illary bones, or provided with rude teeth, soasetimes
merely  serratures in the  bone which reach the
posterior edge of the mouth,  and the upper maxil-
lary bone no longer has any teeth. The foregoing de-
tails will be sufficient to give a complete notion of the
whole class of Fishes. I will show a specimen con-
taining three  fossil fishes.   The scales in the fossil
fishes are precisely the same as in the living  gar-
pike. The s pecimen is from this country—one from
the collection of Mr. Redfield.
   I have now to introduce the class of Reptiles-—
They are animals very dissimilar in their structure
and appearance.  At first one can  scarcely under-
stand the likeness existing between a snake and a
turtle.  Their skeletons in their external form are
so totally different that a common characteristic is
by no means  easy  to perceive.  It seems  almost
impossible that  such  heterogenous  animals  as
frogs, snakes, lizards and  tortoises should  belong
to one natural division ; nevertheless  the class  of
reptiles is the most natural group  of the Animal
Kingdom.  The extreme differences we notice be-
tween the groups just named, disappear more and
more when we examine the distinct types of those
animals which lived in former epochs and are now
extinct.  We have-now some animals which, by
their form, stand intermediate between lizards, or
crocodiles, and tortoises.   We  have other forms
even intermediate between  the snakes and liz-
ards.  Tbe common snake has no feet; numerous
ribs extend the whole length of the body.  The
numerous vertebras have each a pair  of ribs, and
the structure is so uniform that in a transverse sec-
tion in any region  of the body, we see precisely
the same arrangement of the bones and soft parts.
   8ome lizards, like snakes, have no feet.  In some
there begin to appear on tbe sides  and underneath
the abdominal cavity rudimentary feet, or ribs,  at
the extremities of which there is a hook.  First
we observe  these enlarged—then there are two
fingers—then some rudimentary feet on the sides
of the  head with one, two, and  afterward three
toes, until we have the common form of feet with
five distinct  fingers.  All  possible  intermediate
states between tbe existence of feet and the com-
plete want of them is known among the living rep-
tiles—snakes and lizards.   The length and propor-
tion of the  body  vary.  Some are  of extraordi-
nary length;  in others, in which tbe body is shorter.
the tail is more separate from the botly and forms a
long, tail-like appendage.
  There is no longer any difficulty in tracing this
form in that of the turtle, in which the body is broad,
flat, with very short tail and neck. Here we have
a type  where the tail is very long and very similar
to a snake's  body, and here we have feet of con-
siderable size.
  Again, in the  frog the legs are of extraordinary
length, being in  many  instances  longer than the
body.   The  medial region is broad, flat and short
as in turtles, so that the external form, where we
trace all intermediate forms, should no longer be  an
objection to the  union of all these animals in one
group.  But in the intermediate forms we have pos-
itive characters by which they all agree and there-
fore must be classed together.
  These characters are—first:  the structure of the
heart.  In this injected heart of a turtle you see
two red cavities in which the blood comes from the
lungs, and this  black  cavity from which the blood
is forced into tbe lungs and other parts of the body.
The heart of reptiles is divided into three cavities.
                       Let that be the ventricle
                        irheart proper: from the
                       auricles   arises a  large
                       blood-vessel proceedingin-
                       to the body of the animal
                       and also sending two ves-
                       sels to tbe lungs.  A large
                       Itrunk arises from this cav-
                        ty sending  branches  to
                       [the  respiratory  organs.
                       The main trunk,  which
                       carries the blood into the
                       body,  divides into  nu-
 merous branches,  supplying the head, anterior
 extremities  and alimentary  organs, and also the
 viscera iu the posterior extremity.   That blood
 returns and enters one of the auricles, while the
 blood  which  goes  to the  lungs will  enter this
 other  auricle, so that the blood from the body
 is mingled in the common ventricle. Thus we have,
 going to the body, blood of a mixed nature.   That
 which has become blood and has lost its vital prop-
 erties  by being  used  inthe body, returns to one
 of the  auricles ;  and  tbe blood which has become
 oxygenated in the lungs comes  back to the other
 auricle. The venous and arterial blood then empty
 into this common cavity, the ventricle, and are forced
 thence into the body, as well as tbe respiratory  or-
 gans.   Such a circulation is that which is fonnd  in
 all cold-blooded animals.
   In the higher  animals the blood  which comes
 from the body into this cavity passes into that, and
 does not unite with the arterial blood, but is forced
 into the respiratory organs by a vessel distinct from
 that, and from the lungs comes(~
 back into this cavity, and from!
 this into that, so that the blood]
 coming from the body  and  res-]
 piratory organs  never mingles.
 This is a double circulation pe-
 culiarto wsrnt-blooded animals.]
   Reptiles are cold-blooded,tbel
 temperature of the blood never!
rising higher than that of the*
 
46
surrounding atmosphere.  Their temperature sinks
with that  of the atmosphere, and when it is very
low  the  animal becomes  torpid  and  remains
so during tbe cold season. Turtles, snakes, liz-
ards and frogs sink into this state during tbe Win'
ter, and their circulation is very much diminished.
  All reptiles breathe with lungs, which are of a
very peculiar appearance.  I have here the lung
of the snapping-turtle—it is sponge-like and full of
large air-cells.   The air enters into  tubes  or
air-pipes, which unite in one tube opening into the
               ■mouth and communicating with
               |the nose.  Here is the lung of an-
                other  reptile, the boa-constrictor,
                [in which the cells are beautifully
                ■more numerous and not divided
                linto larger cells.  These two rep-
                stiles have such organs of respira-
                Ition.   We  have seen in fishes
                ■only a rudiment  of a  lung—the
                lair-bladder.   Here we have the
lung of a reptile, into which  the air is  constantly
introduced,  moving  in  and out as  often as the
animal requires  air:  but the inspiration is not
so frequent  as  in warm-blooded animals, and the
quantity  of oxygen  consumed is  much less.—
These two characters are  sufficient to distinguish
reptiles from all other animals, and to show that,
notwithstanding their  extraordinary diversity of
form,  they  are a very  natural  class in  their
structure.
  Without entering into asy more  anatomical de-
tails, I  would mention  some  peculiarities of the
different organs.
  Reptiles have been divided  into four orders—
Turtles, Lizards, S?iakes and Frogs.  The first are
named from the Greek Chelonias, the second Sauri-
ans, the third Ophidians, and thefourth Batrachians.
These terms simply signify the same as tbe  com-
mon name, and are only used for the sake of a com-
mon understanding  in  different langaages.  The
common name is just as good, only it would some-
times create mistakes.   For instance: here is a fish
called the gar-pike, which has a namesake.belong-
ing to a different family.  So it is necessary to have
scientific terms  derived either from the Greek or
Latin—for scientific men of different nations speak
different tongues, and it is essential to a thorough
study or knowledge  of tbe different types of the
Animal Kingdom that there  should be  a fixed
Classification, as the names in common use among
us  would  necessarily  change  with  different
languages.
  The order of Chelonians is peculiar from the singu-
lar form of the body.  The common turtle is covered
with large flat cuirass-shaped scales, both above and
below.  These  scales rest immediately upon the
bones.  JThe question is, what are these bones ?—
                          ... Turtles have been
                            considered  as  ani-
                            mals of a peculiar or-
                            der, constructed on a
                            different  plan  from
                            other animals,in hav-
                            ing  their  skeleton
                            outside, and  having
                            bones analagous  to
                            no other animals.—
                            But it is easy in com-
                            paring to find what
                            the broad, flat bones
                            are. Here we have
                            the indication quite
                            plain:  the  whole
                            space  between  the
                            scales is not filled up.
[Prof.  Agassiz's  Lectures.

               In all marine animals the ribs do not enlarge the
               whole lepgth but are only united near the back-
               bone.   The large, broad disc is nothing hut a lo-
               ries of ribs, and when looking internally they pre-
               sent  precisely the) same relations to the  central
               backbone as in common vertebrated animals.
                 In the philosophical comparison of animals the
               mere disc is not sufficient, but will lead to frequent
               mistakes.  On the anterior portion  of the  animal
               we have ». similar series of bones something analo-
               gous to those of the crocodile.  The  anterior  ex-
               tremities of tbe  ribs unite in a series of  middle
               bones, called sternal bones.  The lower cuirass of
               the turtle is nothing  but a series of those bones
               formed in tbe  same  manner as ribs.  The whole
               middle region  of  the  body is thus immovable  be-
               tween them.   There is no possible motion  of  the
               ribs or sternum.   In some  turtles only the ante-
               rior and posterior portions are  movable, and  the
               animal has a head of most extraordinary form.
                Here is a head of a large green-turtle.  From
              the cavities in it one might suppose the animal had
              a large brain—but it is not so.  Here is a little hole
              through which the spinal marrow passes.  These
              large covered cavities are only to protect the large
              muscleswhichmovethelowerjaw. Sothatwehave
              a covering formed by the skull to protect the lateral
              muscles which  move the lower jaw.  The head is
              large, but the space for the brain small.  So ia rep-
              tiles, the brain is  not very large,  and we have in
              this class the same relative position of the different
              parts of the brain.  The little quantity of  brain re-
              mains uncovered by the  anterior lobe.  The only
                                       progress in the form of
                          the brain is that the an-
                          terior lobe of the brain
                          is larger than the other,
                       __but the posterior part is
still uncovered by it.
  These  turtles  form a  natural group.  They did
not exist very  anciently—we  do not find  them
beyond the oolite period, but  we find tbe next
order, the Sanrians, at an earlier age, immediately
after the  coal era.  The  question  arises, Are the
saurians, which  are  found  below  the oolite and
above  the coal, real lizards 7   Tbey have been so
considered, but I think the analogy with lizards
has been exaggerated.   In fact  all the reptiles
found in the strata below the chalk have a pecu-
liarity which the actual lizard has  not:—the teeth
are inserted in cavities.  Lizards have teeth united
with their jaws,  but  these  ancient saurians  have
teeth inserted by a long root into a  cavity ; and we
have the  same structure in the crocodile ;  so that
the analogy between the crocodile and  lizard
which  was  considered so natural and close, is, I
think, rather exaggerated.  I consider crocodiles
as one remnant of those ancient types of large liz-
ards  having, like  reptiles, teeth inserted in the
hollow cavities of the jaw. You see in this head
of an  alligator the character of their  teeth very
plainly.  Most of them have fallen out, but in the
few remaining you see a long root projecting above
these   cavities.   Among lizards  we have  teeth
which unite with tbe head and there are never any
such cavities for their reception.   These  reptiles
should  be called Rhizodonts—having  teeth with
roots.
  I will mention the distinguishing characteristic!
of the alligators^-
of the  South.
from the  croc
odiles  of  the
East.   You se^
the teeth of the
lower jaw come
within the  up-
 
,e  Animal Kingdom.
47
per jaw,  and when the jaw is closed they unite |
m such a manner that only the teeth  of the upper
jaw are seen outsideof the lower.  In the crocodile |
proper  you  have the  teeth   closing in  a  dif-
ferent manner,  crossing  each other,  so that on
a  tide view you  see two  sets of teeth—those
of the  lower jaw coming  outside those  of  the
upper-  It is a fact for which  we cannot  account
that all the crocodiles of the Old World have teeth
varying in this manner from the  alligators of this
fontinent. There is one  species, however, in the
West Indies constructed on the plan of the Eastern
crocodile.
  With  this type  we have to combine fossil
reptiles,  of which portions only  are  known.—
They havs been described chiefly by Conybeare,
Prof. Owen, and other British Naturalists.  It is in
the oolitic series of Great Britain  that they are
mostly found.  They are  truly gigantic, some of
them exceeding in size the largest terrestrial mam
malis.  Only parts havs been restored.   They are
described under the  name of Plesiosaurus  and
Ichthyosaurus.
  I will only ailuds to another of these types, of
which I have some  fragments, the precious gift of
                      _Dr. Torrey.  Here  is a
                      (fragment of a  tooth,  por-
                      Ition  of the jaw, and some
                      ■rudimentary teeth coming
insideways.  These teeth are larger than any of
those in  the jaw of the living crocodile.  You see
tbe portion of the tooth is larger  than the whole of
the other.  Therefore we are  allowed to infer that
this animal was much larger than any of the largest
alligators of this country.   This would be one
of those  large  reptiles.   It belongs to the genus
Mososaurus, found in  the cretacious strata of Eu-
rope.  The peculiarity of the teeth is this: Let that
be  a portion of  the jaw.|
Here is a large cavity fot
the teeth, which are  gone
Here  is a root of a tooth!
broken away, but the root
is united with the bone so that it is :iot fully sepa-
rated  from the bone;  but that it  was, at the  time
            |whe» the tooth was formed,we see by
            ■the fact that so  much of the tooth is
            (preserved.   Back of this  there  are
            ■the small teeth coming out whose pe-
            Iculiarity is  to take  that form.  They
            ■have two sharp edges. This is a trans-
            Iverse section.  The vertebras  are of
considerable size.  Here you have one of the back-
bones. The appendages aboveand below are broken.
Tbe back-bone of the fossil is twice as large as
that of the largest crocodile.  How can this be as-
certained to be a reptile? It is easy.  Youhave these
hollow surfaces.  So this simple bone can be referred
to the class of reptiles simply by the character of tbe
articulating surfaces of the vertebra.  That it is a
reptile and not a fish is ascertained by thefactthat
the appendages were united to the  vertebras, as is
seen  by these fractures.  We  may ascertain to
what genus it belongs bythe  peculiar form of the
joints of the vertebras, which  [as seen in the  next
diagram] are obtusely triangular. The articulating
surfaces, though concave onone and convex on the
other side,  are  usually]
triangular, and that is tin I
peculiarity of the genus|
Mososaurus.
  It is by this simple pro-l
cess of  comparison thati
the characters may be determined, and if any one
will investigate all  the  relations between  such
bones and skeletons  of a reptile, he will himself
be  able  to  restore the  entire animal, giving the
whole outline with great accuracy. g^_.
  The number of fossil bones coming to Wght every
year is so great that there is a greater field of in-
vestigation  than  there  are  students to  enter it,
which should be  an inducement for many more to
begin  such studies.   In  this country, fossil bones
have been studied but very  imperfectly.   The
Mastodon has been discovered here, and I have no
doubt there are as  many bones remaining unde-
scribed as  there  were several years ago in many
countries of Europe, so  there is ample room for in-
vestigation.  Owing to tbe before-mentioned pecu-
liarities in the  structure of the crocodile—the form
of  the teeth and modifications in the vertebrss—
those ancient types should form a peculiar order by
themselves.
  The order of lizards,  so numerous in our  day, is
of  little geological interest,  because so few fossils
have been found to compare with existing types.
  The next order is Ophidians.  Having  shown
how gradually this  order passes  into that of liz-
ards by the formation of tbe feet, the inquiry arises,
By what are snakes distinguished from lizards 7
for there are lizards without feet, and snakes have
rudiments of feet.  In  lizards the lower  jaw  is
movable in its articulation on the temporal bone,
 and can only move up and down.   In the snake the
same motion is possible,  but the two jaws in front
can also move sideways, so  that  the jaw can be ,
separated considerably, and thus the month ean be
enlarged indefinitely.  This is the  reason  why
snakes can swallow animals  of a  larger  diameter
than their own body. Not only is their mouth en-
larged  in that manner, but the posterior articula-
tion of the jaw with the head is such, that the jaw
can slide on the aide of the head, and thus enlarge
in  that direction.  The temporal bone is  detached
 from the skin, and forms the joint of tbe lower jaw,
which joint is movable right  and left, allowing the
 snake to distend its mduth enormously.  But the
upper jaw is also movable, and iu some, as in ven-
omous serpents, there are movable teeth, uniting
with the sac containing the poison which they in-
ject through tbe tube of the tooth into the wound
made by the bite of the reptile. ■$*»■■■•'*-•    y______
   Snakes have existed in former times. Prof. Owen
has ascertained that in the London clay, fossils are
found  allied to the boa-constrictor, as early as the
deposition of the most ancient tertiary bodies.
   The  last family is  the Batrachians, which is so
interesting in  its geological bearings,  and also
anatomically frem the extensive metamorphoses it
undergoes, that I beg leave  to pass by the class of
birds which is so well  understood  and  is of less
interest, and take up the order of  Batrachians for
the next Lecture. 
48
Prof.  Agassiz's  Lescrctv.
LECTURE  XL
Examination of the Order of Batrachians—Their  Metamorphoses the Key to a proper Classification  of Animals
   in the Scale of Being...The importance of this key. or principle never as yet known and applied.... Fossil Batra-
   chians illustrate this principle.... Birds and Mammalia—Difference in their respiration....Cause  of the power
   of flight in Birds___Peculiarity in the Toes  of Birds—A Clue  to the Discoveries of Ancient Forms by thait
   Footprints___Pres't  Hitchcock's discovery—Hisjopinion sustained...Diversities in  the class of Mammalia....
   Whales  an ordar of Mammalia—Fossil  Whales___The Hydrarchos...Herbivorous and CarnivorousAnimals—Dif-
   ference in their alimentary organs___The teeth of Rodcntia—The jaw of the Badger.. ..Motions of the jaw In ani-
   mal)—Teeth of the Barbaroussa___The Pachjdermata---Remain' of a species of the Elephant in Frozen regioai
   with the flesh preserved___Sudden change of climate in th « Frozen| Regions___The Mastodon of  reoent data
   —The Ruminantia—The Rodentia—The Singular character of  the Didelpfiides—The Carnivora—Seals: Car-
   nivora  proper___The  Quadrumana—Difference between a man and monkey.
   Ladies  and Gentlemen: In the  examination
 of the class of Reptiles,  we  have already  gone
 through four orders—viz : that of Rhizodonts, con-
 taining those gigantic  fossil extinct types and the
 now  living Crocodile;  second, the Chelonians or
 Turtles; third, the Saurians or Lizards; and fourth,
 the Ophidians or Snakes.
   We have to-night to examine the order of Ba
 trachians.  These animals are very numerous, and
 of a  singular character, owing  to their mode of
 growth.   Tbey differ from the  other reptiles  in
 this—that their body is  naked, without scales, and
 the skin is soft.  But  what  is  the most striking
 feature in  their character,  is that they undergo a
 series of changes during their life after they are
 hatched.  The young batrachians all have a long
 tail, like lizards ; even frogs and toads, whenyoung,
 have  this appendage.
   The order of Batrachians contains Frogs, Toads,
 Salamanders,  and  many  other animals allied  to
 Salamanders.   There is an extraordinary difference
 in their external form, though all agree in this, that
 after  they have escaped from the egg  they have a
 long tail circumscribed  by  a fin, and in their  early
 stage they have no feet.  Soon after  they are
 hatched, the feet begin to appear, and in some the
 tail disappears, and they  assume the short, com-
 pact form of the frog and toad—while others retain
 their  tail.  Again,  when young they all respire
 through  gills, which some  lose, in later  life, and
 breathe through lungs like  other reptiles.
   In these tew facts we have a  most important in-
 dication  of the value of character throughout the
 great division of  the vertebrated animals.   If my
 object was not to illustrate the principles of Zo-
 ology, I would enter into more details in the ex-
 amination of the different  species and their exter-
 nal characteristics; but these can be learned from
 books.   In these facts of the structure and charac-
 teristics  of the Batrachians, we have illustrated
 some  fundamental principles of classification—and,
 in fact, a new principle  which I consider as  most
 important for  that  object.   Animals have usually
 been  classified by the difference in their structure,
 which principle is perfectly correct;  but the diffi-
 culty  is to ascertain by  a knowledge of their struc-
 ture which combination of organs—which struc-
 ture^—belongs to the higher and which to the lower
 order. We have had no test for ascertaining this.
 The good opinion men have of their own superiority
 over the rest of the animal creation, has induced zo-
ologists to consider those animals more nearly allied
 to Man to be the higher order, and those that differ
 more  widely from this type to belong to the lower
 orders. But the actual scale by which we measure
 the degree in the gradation of animals is found only
 in their  metamorphoses; and  unhappily this test
 has not been introduced into our classification as it
 should have been.   The facts we know already in
 relation to the structure of Batrachians  and their
 metamorphoses are sufficient to give a perfect key
to the classification of the two lower classes of ver-
tebrated animals and the succession of any order
even with the most minute details.
  In this diagram I will sketch not  any one parti-
cular animal, but tbe general  outline of a group
When the young batrachian escapes from the egg
the general outline is elongated, with a tail, but
without legs
and we then have the form of a Salamander.  Then
the legs will increase in size and the tail will dis-
appear—and we will have the form of the frog and
toad.  In the beginning there are external append
ages for respiration—the gills.   These  disappear
entirely in the salamanders,  frogs aid toads, and
remain permanent in the others. The earlier stages
in the growth of the animal will be considered to be
very analogous to the lower grades of animals—and
in the full-grown state, to the higher.  Let us see
what are the relations of these to other vertebrated
animals.   Is it among birds and mammalia that w«
find an analogy to  these animals?  Certainly not
It is among the fishes we have a similar structure.
Therefore we shall  consider fishes as  lower than
those reptiles which begin  with the characteristics
■een in fishes, and progress  to  a  higher develop-
ment.  Here is evidently a  test by which we know
that the class of fishes should stand lower than rep-
tiles, which, otherwise, might be doubted.  The fact
that some respire by gills, is  not of itself sufficient
evidence that tbey stand lower or higher.  There
are some reptiles that breathe  by gills their whole
life.  The fact of  the fish-like forms in the young
batrachian is sufficiently indicative of the po«ition
which fishes should occupy with reference to  rep-
tiles and other vertebrated animals.
  Let us again examine the different families in the
order of Batrachians.  We have  some families in
which the form is thus:
 
The  Animal Kingdom.
49
First external gills, and, having lost  them, a very
minute fin appears, and afterward ill-shaped, im-
perfect feet.  Then in some, whose body is larger,
we will find the fingers  more complete and the legs
more developed, and larger and more complicated
s	■$$■#;*! - '■ V-	
n'£'		
feet.  In others the tail will gradually shorten, and
the fin circumscribing it will  gradually disappear.
The gills at length  will disappear, and the legs at-
tain such a size as  to become  the main organs of
locomotion.
  Here, then, we have—in such a series and grada-
tion of forms, and in such a relation between these
forms and  the changes which the frog undergoes—
the actual indication of the order of classification in
the arrangement of all the families. And  wher-
ever Embryology—the knowledge of the changes in
the young animal—has taught us the successive
forms, we may have in these changes  important
hints as to the classification of types.  Therefore I
think the principle ot metamorphosis, as a founda-
tion for classification, is the best and most striking
guide a zoologist can take   But. as I have said,
this principle has been very imperfectly understood,
and in fact never applied as one upon which classi-
fication in general could rest.
  There are several fossil Batrachians, and what is
again interesting, is that the larger ones and those
which have appeared  earlier, belong to the older
tertiary strata.  It is in the more recent tertiary
beds we find  those which  show a closer affinity
with frogs or tailless batrachians.
  I will not enter  into farther details.  My object
in speaking of the Batrachians was to illustrate the
principle of classification, derived from a knowledge
of the metamorphoses in any portion of the Animal
Kingdom.   In  another Lecture I shall show that
this principle will be of direct  application in the or-
der of succession of the different types of the Ani-
mal Kingdom.   Though we have not investigated
all classes,  there  are  sufficient facts obtained to
■how, even now, that this is a fundamental  princi-
ple upon which classification can rest, and that this
same principle is the one in the order of succession
of types in all geological ages.  (Applause.)
   The next class is Birds, and next the Mamma-
lia. These two classes have certain characteristics
in common, of which I will first speak.   They are
 both warm-blooded animals, and they both breathe
 with lungs.  Birds, as well  as Mammalia, have
 large air-sacs called lungs, which open externally
through the mouth as well as the nostrils, in the
 same manner a* reptiles ; but there is this funda-
 mental difference between reptiles and birds and
 mammalia.  The  latter  two  classes are  warm-
 blooded.   The  difference  in  temperature  is un-
doubtedly owing  to the greater amount of oxygen
consumed in respiration.           ....
   Mammalia  and bird, agree again in the large
 size of their brain in proportion to the body.  It is
 ■o much greater  than in reptile*  as to be quite
striking   In comparing, for instance, the brain  of
the sparrow with  that of the largest sea-turtle, that
 of the sparrow is  found to be about half the size of
 that of the tnrtle.   The difference in proportion to
 tbe size of the two cla.ses is  as 100 to 1.
   The peculiar characteristics of the class of Birds
are that the anterior and posterior extremities  are
entirely dissimilar.  The  former are  wings—the
latter  legs.  Nevertheless the  structure  of  the
wings and legs in birds is  precisely tbe same—the
bones exactly correspond,  and the  true difference
is owing to their arrangement.  The large thigh-
bone, uniting with the back-bone, corresponds to
the shoulder.  The thigh-bone corresponds to the
humerus—the leg proper corresponding to the fore-
arm—then the foot and fingers correspond to  the
hand.  These parts are covered with feathers,  and
the difference which is obvious in the bones entire-
ly disappears in tbe external limbs. This analogy
in the anterior  and  posterior extremities  can be
traced throughout the great type of the vertebrated
animals.  The short fingers on the foot of the bat,
correspond precisely to the long fingers ef its hand,
even  to  their arrangement and number of bones,
and the difference is only in the manner  in which
they unite together by membranes.

  There is no class among  vertebrated animals so
uniform as birds. What I have said applies to tbe
                  whole class—they differ  only in
                  the shape  and  form of the  bill
                  and the fingers,  and ia the pro-
                  portion  of their bodies-  In  the
                  parrot, which is widely differ-
                  -nt from the ostrich,  you  will
                  lind the  same  neck and back
                  bones,  tbe  same  arrangement
                  if the wings and even  the same
                  lumber of  articulations in  the
                  toes.
                   In their respiration, they differ
 runi Mammalia. Birds, in order to fly, must necessa-
 arily be very light. To obtain this, they  are provided
 with a large air-sac, extending from the lungs  into
 the abdominal cavity, and even into the bones. The
 bones  of the arm in birds  are hollow, communicat-
 ing with the air sacs of the lungs.  The reason why
 a bird falls when its wing  is broken, is because the
 air within the cavity no longer resists  the pressure
 of the chest.  If you sever the bone of the wing,
 you will hear the air whistling through the broken
                     bone.  It is owing to this ar-
                     rangement that the specific
                     weight of birds is so much di-
                     minished, and they are ena-
                     bled to soar  through  the  air
                     with such ease.
                       Only  a few birds  are de-
                     prived ef this faculty—sueh
                     as the ostrich. In this the ster-
 nal bone is quite flat and withoui
 the  peculiar projection  which  is
 seen  in other birds, to which the
 large  muscles  are  attached  thatl
 move  the  wings.  I  will draw  nl
 transverse section of the breast bonel
              of the  ostrich.   Thel
              surface is entirely flat!
              and here is  the cavi-"
              ty for the lungs—here are the ribs and
              here the breast-bone entirely flat.  In
              otherbirds there is the same arrr.nge-
 mentof  the ribs and breast-bone, and there is a large
 ridge rising  from the middle, and tol
 it are attached the broad muscles!
 which move the  wing.  These mus |
 cles are well known as  the  whit.
 meat  of the fowl.  There is a eon i
 stant  proportion in  the  extent  oil
 this bone  and  the power of flight!
 in all  birds.  I  will enter a  littk-l

 farther  into details.  Let this diagram represent
 
50
Prof.  Agassiz's Lectures.
             the backbone and ribs attached to it.
             I There are additional bones not found
             m other birds, passing from one rib
             jo another, preventing the compres-
             sion of the chest, which would other-
             'wise modify  the  respiration, by di-
minishing the quantity of air inspired.
  I have mentioned that the fingers, or rather the
toes, were similar in all birds.  I will pursue this
point, as it is the only one upon which birds  have
acquired a geological interest.  Many years ago
Pres. Hitchcock of Amherst College discovered cu-
rious tracks upon certain rocks in the  Connecticut
Valley.  He examined these impressions and pub-
lished  some  diagram* of them, maintaining that
they were the  footprints of birds.  I believe this
assertion was received with as  much  incredulity
in this country as in Europe.   He has for years
been struggling against opposition in  reference to
his assertion.  To himself, as well as to a few in-
dividals  who had confidence in the fixity of the
laws of Nature, the evidence was satisfactory. At
length his views have been fully borne out.  It can
be proved with as much certainty that birds  have
existed as early as the deposition of the new red
sandstone, as if we saw them—Lhough only the
tracks remain, like  those left on a sandy beach —
These tracks were made long before Man was
created,  and  the evidence is beyond the slightest
doubt.  (Applause.)
  Tbe evidence is this.  The toes  of birds are
always two.three or feur in number. When there are
four there is one behind corresponding to the thumb.
Let this represent tbe foot.
  1 n the posterior finger therel
is one bony articulation and a!
nail—inthe  first  finger, two(
bony articulations and a nail
—in the second, three articu
lations and  a nail-joint—and!
in the third, four articulations^
and a nail-joint.  There is not
another animal in which  the!
number of articulations is such as  in birds.  Here
we have only three fingers.  The first has three, the
second four,  and the third five articulating joints,
including  the   nailjoint.—;
In the only  bird which hasj
two  fingers,   the   African
ostrich, the first finger has foui
and the second five joints.—
Now in the new red sandstone]
of the Connecticut Valley, the(
impressions left show plainly|
the joints of the toes and num
ber of articulations, which cor-
respond precisely to the fore-
going arrangement.  This is satisfactory evidence
to every anatomist that the impressions were from
birds only. I do not maintain by this that President
Hitchcock has  shown that they  were all birds'
tracks.   There  were  also  impressions of other
animals whose  tracks do not agree with those of
the birds. But there are tracks of birds running over
wet sand, that have been preserved by a deposit
of mud upon it, which is enough  to prove conclu-
sively to the mind of the geologist the existence of
animals—though there are no remains at all. These
results are satisfactory, because they promise more
information concerning the true history of geological
succession on the surface of the  globe.  Since the
ripple marks of the  ebbing tide, and  the slightest
impressions of the feet of animals can be recognized,
we have evidence that the time will come when
we shall know all that has transpired  on the sur-
face of the earth, at a period when  Man did not
exist, and we can reconstruct the form of the whole
Animal Creation only by these slight evidencei.—
(Applause.)
  The last class of vertebrated animals of which I
have to speak,  is the Mammalia.  It is a clasi
in which the types are almost as diverse as in rep-
tiles.  We have, in  this  class,  animals provided
with fins, others  with feet, and others with wings
There are some which have external horns of large
size, some with smooth skin, and others covered
with hair.  Though their  external  appearance is
extremely different, they all  agree in this reepect:
they have warm  blood, like birds.  But they have
no air-sac extending into other cavities of the body.
The breast is  divided  by  a  large partition  called
the diaphragm,  which  separates the respiratory
cavity from that in which the other viscera are con-
tained.
  Birds lay eggs, while the  Mammalia bring forth
living  young.  It is  upon  this  mest  important
difference in their character that  the reunion of so
many animals  so widely different has been  deter-
mined.  For example, the  Whales as well as bats
bring forth living young and nourish them with
milk.  The similarity  of their general structure ii
closer than would appear—owing to this  peculiari-
ty.  The internal structure  of the whales  is the
same as the higher Mammalia,  and though they
have been considered as fishes they have no affini-
ty, but only anexternal analogy to that class. The
whales are really much more allied to Man than to
any of the fish tribe.
  The distinction between  analogy and affinity is,
that the former indicates only an  external similar-
ity ; but the moment we investigate the internal
structure of the whale we find such a striking re-
semblance to the Mammalia that we call it affinity.
So then whales are analogous with  fishes, but are
truly Mammalia.  Even this  analogy wtih fishes is
much less  than  it might appear.   They  have
fins, but for  a   different  use from fishes.  In
fishes the large fin at the end of the tail ii placed
perpendicularly, and cleaves  the  water from right
to left, producing a forward motion  only—while in
whales this fin is placed horizontally, audits motion
causes the animal to rise or sink at will.  And this
arrangement facilitates their respiration, for they
cannot breathe except in the atmosphere. Fishes
can rise and sink, but only slowly, on account of the
perpendicular  position  of the tail; but whales can
rise rapidly to the surface to breathe  the atmog-
pheric air.________
                                 This is theskull
                                >f a dolphin, one
                                ifthewhaletribe.
                                It is widely dif-
                                ferent  from the
                                lass of fishes and
                             __lis  provided with
uniform  teeth.   The  whales are, however, the
lowest order of Mammalia, as  is indicated by the
structure  of their other extremities.  They have
anterior feet, but no posterior.  They have finger*,
five in number, as in other Mammalia, but united
by a thick membrane forming a fin.  The structure
of the caudal appendage, and in some of them the
existence of a dorsal  fin,  shows some relation to
fishes,  which puts them in  a  lower grade, but «till
their true affinity is with Mammalia.
  Whales have existed in former  times.  Most ex-
traordinary sized fossil types are found in the South
ern parts of this country.  In Alabama large speci-
mens have been discovered,  which  unfortunately
have been described by an ignorant German natur-
alist as the remains of reptiles, and this discovery
of so much importance, has been leuened in  inter-
est by the unscientific manner in  which they were
described.   Bat lately Prof. Wyman, a yoasg nat-
 
vThe Animal  Kingdom.]  |
51
aralist of Boston, and Dr. Gibbs of South Carolina,
have given a scientific description, showing  their
essential structure to be that of Mammalia.  And
Still later, since their proper place has been assigned,
a skull has been discovered, showing the peculiar
rounded form of the posterior part of the head, giv-
ing another evidence that the remains are those of
a specie* of whale, and not those of a reptile called
the Hydrarchos.  The existence of whales dates
as far back as tbe cretaceous epoch,and many have
been found in the tertiary strata.  There is a diffi-
culty in determining the species of these fossil ce-
taceans, on account of their large size.  It is much
easier to compare smaller specimens.
 The Mammalia are divided into two other large Or-
ders beside that of whales: the Herbivora  and  the
Carnivora. There is a difference in those which live
on vegetables and those  which devour animals for
food.  The form and structure of the teeth for grind-
ing vegetable food and for cutting  and devouring
living animals—as also  the  alimentary organs  for
digestion, which require the food to undergo a pro-
cess of assimilation—are very  different in the two
Orders.  The difference  between the food and  the
substance  of  the  body of an herbivorous animal
and the modification it has to undergo to become
assimilated, render the digestive organs much more
complicated in the herbivorous  than in the carnivor-
•u* tribe.                                  **JM
  Again, the food of these two orders is so different
in the various families,  that we find numerous  far-
ther modifications in the operations by which the
food is prepared before it is  swallowed. We  have,
for instance, in the gnawing animals teeth entirely
dissimilar  from those which  act upon the surface of
                        '.he  jaw.   This is jaw
                        J if the beaver.  You see
                        jthe  two anterior teeth,
                        [both in  the upper  and
                        "'ower jaw. Then there
                              space deprived of
                        Iceeth, and  in the pos
                        Iterior portion of the jaw
We have the grinders.   Animals with such jaws,
and they are  very numerous, are  called Rodentia.
Rats and  squirrels are of this group.  Rabbits  and
hare* have two anterior teeth in the lower jaw,  and
four or five grinders on the right and left side of the
posterior part of the upper and lower jaws.   The
                      """"Itirst are called  incisors
                        land the second molars.
                        ]We  find  such  only
                        jamong herbivorous  ani-
                        |nals, while in the  car-
                         nvorous we find a third
                        Ikiud of teeth :  In  the
                        Ijaw  of the  tiger you
                        Jaave  in  front  the  in-
                        [cisors,  and in the pos-
                        terior part the  molars ;
but beside these, in  the anterior position and on
the sides, there are four  large  teeth, called  the
tanine teeth.   They are those with which the
animal seizes and retain* its prey.  In the badger
the articulation of the lower jaw is so powerful that
the jaw cannot fall.   There i* a groove into which
the enlarged end  of the lower jaw is introduced,
and closed by the  upper so strongly that they are
kept in their natural position, and even after the
soft parts are removed,  the jaws cannot  be dis-
joined.
  All carnivorous  animals can make ouly upward
and downward motions of the jaw, with  a very
slight lateral  movement, while those  which live
upon grass have,  beside  these, a lateral motion.—
This is especially evident in  ruminating animals.
All the herbivorous animals which have a compli-
cated stomach, from which the food is returned to
the mouth te be ground over again, have no  canine
teeth—only the large molar teeth, with no incisors
in the upper jaw and five  in the lower.  Deers,
elks and cows are of this family, having no incis-
ors inthe upper jaws, and no canine teeth at alL
  When I say no herbivorous animals have canine
teeth I suppose many have thought of the extraor-
dinary tusks of the elephant, which are placed in
the same position as canine teeth in other animals.
In this head of the Barbaroussa  appear  canine
teeth of extraordinary size,  but you will readily
perceive tbe difference between these and the ca-
nine teeth  of carnivorous animals.   Tbey are not
used to seize the prey.   They are curved upward,
and are used for other purposes, beside being an or-
nament to the heed.  In this head of a ho ar. from
the Island of Bor f>V£Z,:Z.;
neo—the BarbaJfa*
roussa—they arc'^v,-,
curved like horns.fejg
Tn the  elephantWjt*
theybecomelarttej '
tusks, correspon
ing to the canine
teeth, but are notj
used  to perforoij
the office of cauitu
teeth as in the Carnivora.
  Among the Herbivora  we  will  first distinguish
the large family of Pachydermaia, in which the fin-
gers are covered with a hoof.   The horse, the
elephant and the rhinoceros belong to this family.
They have grinding teeth of a large size.  Some
have many and some very few. The elephant, the
largest of the Mammalia, when full grown has only
four molar teeth—two in the upper and two in the
lower jaw.  The young elephant has twice as ma-
ny—four in the lower and four in the upper.   This
differpnce is  easily explained. The new teeth are
                         itiot formed under  the
                         old ones, but behind,
                          md as they grow they
                          uove forward, first the
                          interior portion of the
                           K)th  appearing above
                         r|ie bone of the jaw,
                         r.:ie  posterior  portion
                         ieing  still   covered
                         with  bone.  As they
 
52                            Prof Agassiz's  Lectures.
come forward they displace the other teeth, the an-
terior por-.'on successively falls away and the pos-
terior comes in gradually.  In the  full-grown ani-
mal thero are only four maxillary teeth in the whole
jaw  and two tusks, making six; but these are re-
newed constantly, so that after the second pair has
taken the place of the first,  another will be formed
behind. So it  is not true that the full grown ani-
mal has only four teeth, for there are new ones con-
stantly forming behind.  They have now eight and
now four teeth,  and when full grown there are only
four left.
  The family of Pachyderms is highly interesting,
because it  is to them we must refer many of the
gigantic terrestrial animals  found  in the tertiary
strata.  They are quite numerous,  and it is these
which have been for the first time reconstructed and
                       ^illustrated so admirably
                        in the immortal works of
                        Cuvier.   We have here
                        the remains of the Pa-
                        laotherium,  an  animal
                        allied to  the  Tapir in
                        the form  of its head,
                        and grinding and ca-
Dine leetli.—Tins aiiiuiai.
the Anaplotherium, is sim
ilar  to  the  Palaeotheri-
um—but  of  a  slender!
frame,  and  the  body indi-
cate* an animal of quickei
motion, while the  formei
was  more heavy and slow.__
The main difference is in tbe  arrangement ot  the
teeth.   There is no vacant space between the in-
cisors and canine and molar teeth of the latter, but
in the former you  see  the  canine  can cross each
other and fill the vacant spaces when tbe jaws are
brought together.  These animals have never been
found entire, but the skeleton has been drawn from
related bones.   Never was even a complete head
found of a Palaeotherium or Anaplotherium.  They
have been reconstructed  even  from much more im-
perfect fragments  than are now  contained in the
Museum of Paris.  The difference in the animals is
notonly in the teeth but also in the feet; the Ana-
plotherium ha* three fingers, the middle linger being
much larger than the lateral ones, while the other
has two fingers only.   The  older pachydermata
found in tbe gypsum are not of gigantic size—the
largest is not greater than the  horse, and some are
a* small a*  an  ass.  But in the more recent ter-
tiary beds,  other genera of  this  animal have been
discovered, such as  the Hippopotamus, showing
tbe same characteristics in the canine, incisor, and
molar teeth. And not only isolated teeth are found,
but in the  Val  d'Arno,  near  Florence, complete
skulls  have been  found larger  than the largest
specimen* known to naturalist*, and most of these
are preserved in the Museum  of Paris, which con-
tains the largest and most complete collection o!
fossils.
  Several species of the elephant have been found
—and what is  most remarkable, they lie in the
coldest regions of Siberia and  tbe most arctic por-
tion of this  continent  The  species  is similar to
the Asiatic and African elephant, so that we can-
not doubt that they lived in a much  warmer cli-
mate than  that where tbey are  now  buried—
thereby proving extraordinary change* in tempera-
ture in those regions, and more particularly as it is
evident that they are buried in the countries where
they lived.  The best evidence of this is the fact
that one of these elephants was found so well pre-
served that after disinterring  the body, the flesh
was  actually devoured by  wolves.   These well-
preserved remains  are numerous in the North of
 Asia.  Parras, and more recently Admiral Vrengel,
 when visiting the White Sea, *ays he had to travel
 for  days over remain* of these  fossil elephants
 and rhinoceri and  hippopotami,  gathered on the
 beaches so a* actually to  form hills.  It is  in the
 frozen region of Siberia that the soft  parts have
 been fonnd.  The hairs, skin and even  the muscles
 which are known  to exist,  show plainly that they
 mnst have been  suddenly  buried after their death,
 and could not have been dragged from  the tropical
 regions.
  There is a genus of Pachyderms, tbe Mastodon,
 which is entirely extinct.   It is sometimes called
 tbe Mammoth, but improperly, as that name should
 be reserved for the fossil elephant of Northern A»ia.
 Several specie* of the mastodon  are found in this
 country,  Europe and tropical America.  The largest
 species i* common in this continent and appear* to
 be of recent geological date—so recent that few
 geological phenomena can have taken  place lince
 its  extinction, so that it i* even a question among
 geologists whether this species has not lived within
 the existence of mankind.   This  is a pendant ques-
 tion upon which evidence  i* not sufficient to deter-
 mine the facts.   All this shows how recently such
 animals inhabited tbi* continent,  and how stupend-
 ous the changes that have occurred on  tbe surface
 of our globe.
  Next to the Pachyderms  eomes the family  of
 Rumlnantia, of which the Northern Elk is one. The
 horns of the  elk are flat on the internal margin and
 with projections  on the edges. All the ruminating
 animals are  characterized  by the want of incisors
 in the upper jaw.  There are two groups: those
 which  have  compact horns which fall off every year,
 and those which  have hollow horns which are per-
 manent.  These horns  stand upon a bony projec-
 tion formed of a horny substance, but different from
 the enamel-like substance composing  the  horn of
 the deer. A species of very large size has been
 found.
  The family of Rodentia, containing many minute
 species, among which the beaver is the largest, have
 only two upper and two lower incisors.
  One type in tbe class of Mammalia ha* puzzled
 naturalist* exceedingly, being similar in one re-
 spect to mammalia, and entirely dissimilar in many
 others.  It is the family of Didelphida. containing
 the kangaroo and opossum.  This family ha*  one
 peculiar character: tbey bring forth their young in
 a very imperfect state, and they are afterward intro-
 duced into a large pouch under the skin, where
 they remain till they can provide for themselves.—
 But, except this  common  character and the  fact
 that they have a common  structure of the  brain,
 they differ widely—some having the structure of
 the teeth like carnivorous  and others like herbiv-
 orous animals. Some are,  in fact, carnivorous and
 others  herbivorous, and it is probable that a higher
 consideration than that of food will prevail to make
 these a natural group.  The whole family of these
 Didelphides, except the genus opossum, is peculiar
 to New-Holland, where also numerous fossil specie*
 are found. The opossum is the only species which
 is a native of this part of tbe  New World.  There
 are some few species in South America.  In New
 Holland the  species are quite numerous and ex-
 tremely varied in the structure of their teeth and
 alimentary organs.  The fact that the fossil specie*
 are numerous also in New-Holland, shows that the
opossum has a relation to that type, as  among fos-
sils in that country we find almost none but the Di-
delphides.  Only one has been found in the plaster
of Paris, and no one elsewhere.
  The next group is the Carnivora.  In these we
observe distinctly the cutting canine teeth and the
slender claws adapted for seizing the prey.   This 
The Animal Kingdom.
53
characteristic is particularly strong in the cat tribe.
The claw which terminates  the toes is arched and
■harp »o ai to be used as a fang.
  The order  of Carnivora  contain*  families  suffi-
siently different to be distinguished.  W e have first
the family of Seals, wbich have all the structure of
Carnivora except that their fingers are united to form
fin* and tbe posterior extremities are exceedingly
far back.
  Next the Carnivora proper, which have the finger*
divided, the legs long and the cutting teeth most
strongly developed.  These carnivora  have been
numerous in former ages and do not differ so wide-
ly from living carnivora as fossil herbivora do from
the corresponding living group, and when speaking
of the order of succession in the next Lecture I shall
■how that the nearer we come to the actual types
which  prevail upon the  surface  of our globe, the
less numerous are the corresponding fossils.
  Another family  is the Bats, and differ chiefly by
the form of the anterior extremities.  They have
four fingers which unite by a membrane, while the
thumb is separated and is used as a means of sus-
pending the animal in caves, and for the purpose of
crawling.  During winter they suspend themselves
by their hind feet.
   The last family, the Quadrvmana  or Monkeys,
 begin  to  approach so near  to Man that Linnmns
could not find a common  character  to separate the
monkey from Mankind. (Laughter )   It is singular
that the first naturalist of the  past century, the one
to whom we owe all oar princip'es of modern clas-
sification, was incapable of distinguishing by char-
acter* expressed in words tbe true difference be-
tween »ome of tbe higher monkey* and Men, but
has even placed one species—tbe Chimpanzee—in
the same genu* as Man, under the name of Homo-
lar.  It i*  only by close  anatomical investigation
we can learn the difference.  Now it is easy to un-
derstand it ao as never to mistake a monkey for a
man again.  We have two hands  and two feet.—
Monkeys have four  hands. But,  some  will ask,
what difference is there between the hand  and
foot?  It is not merely the length of the  fingers—
for the fingers of the hand of the fore-arm of some
monkeys are shorter than those of the foot. The
difference  is  here:  We can open and close the
thumb with each successive finger, which we can-
not  do witi our  toes.  (Loud applause )  It is to
this characteristic in tbe human hand and foot that
Man owes his superiority over the lower crca-ion.
The fact that we have two feet  allows us to stand
upright, and while standing to use <rose delicate
organs—the  bands.   Again, this  upright position
enable* Man to move the head freely in all direc-
tions.   The very fact that we have not four bands,
 and that we stand upon our feet, and  in that posi-
tion our hands and head are in equilibrium on our
 vertebral column, moving in all dirertions, give* to
 Man all hi* superiority over the  Brute  Creation,
 both mentally  and physically.
                                      LECTURE   XII.

The Geographical Distribution of Animals-Animals all limited in the'r habitation-Fi.he. «^kA<»s^fUj*
   Atlantic Derfectlv distinct-Species more identical near the Poles, but the identity lost as cney approacn tna
   Equator.P?fPeculiarity of the' Didelphide. of New-Holland.. ..Modification of Tvpesnot caused b^We.A
   group of Fishes peculiar to the Indian Ocean....Different varieties of"Men f™»™"£l%™&£lf£%l?e° are*
   oaries of  Animal Groups.. ..The  Order of Succession of Types ^ ^°^}MT^l'f^„^l^,^^.
   contain different specie.  . .The result^
   ary Strata... .Tertiary Beds... All contain different S.pecies;.. ;;^e  Ouimon tnw                  Order of
   regular gradation entirely fal.e-In view '^/^^^^l^^f^in ths beginning-Illustration, of
   Succession....All the Invertebrated Classes and one Class of Vertebrated touna        s     characterI....A
   this fact... .The first types the highest in themselves... •ReP™e%~'\1™Xbr»ted.. .Man the last type intended
   true  gradation  in the Vertebrated Animals which is not found in the Invertebr.tea....man me  a.,. JVB imeuaia
   —No farther progress to be expected.

  Ladies and  Gentlemen : Before proceeding to
the consideration of the subject upon which 1 in-
tend to »peak this evening, I will  limit myself to a
very few remarks upon another  subject, which I
would gladly have introduced before this time, if it
were not so extensive that I could give no notion
of it without entering into very minute details.  I
mean the subject of the Geographical Distribution
of Animals. It  is, perhaps,  necessary  to  know
something of it in order to understand fully the re-
lation, the distribution, the structure  and the order
of succession of types ; and, as  I have to  intro-
duce the subject of the order of succession of
tvoes  into  this  Lecture, I will  merely mention
the  general results  of the recent investigation*
upon the geographical  distribution  of animals,
without giving the  facts upon  which  these  re-
sults are founded.   I beg you to a cept them as
resting upon investigation as accurate as any that
can be made in the Apartment of Natural History
  Animals  are  all limited in their bab.ta ion  to
some particular spot ou the surface of «'e™be/-
There   are   few  species   existing  over  the
who e exrent either of land or water  These few
species belong to genera in whiehrtis very d, hcuIt
to perceive specific differences andI ,t is  till possi-
blePthat those species which ere th°uSht,.to-,b°  °
widely  dispersed, are neverthele*. to be limited to
some particular spot, when the minute differences
shown in their characters shall have been fully as-
certained and established.  Again : Some which ap-
pear to have been originally so widely diffused
have been scattered over large areas under peculiar
circumstances, which are not natural to the specie*.
But leaving those few species out of consideration,
we  can with  correctness assert that all species
have a  limited habitation, and that mankind only
are differed over the whole extent of the surface of
the globe. There  are  varieties of species in the
coldest climates of the arctic regions, as well as un-
der tbe burning sun of the tropical zone, while there
is  no animal type which is distributed in a similar
manner to the type of Mankind, all over the earth.
The ocean, which is the most convenient mode  of
communication for  Man, has not been  an easy me-
dium for the diffusion of animals from one shore to
another.  What will perhaps astonish some of my
audience is nevertheless perfectly evident from re-
cent invest'gations;—fishes on both shores of the
Atlantic are perfectly  distinct.  There is not one
species found in the Mediterranean which occurs on
these shores:  not one species  occurring on the
shores of France is found south of Cape Cod; I do
not maintain  that there is not one  species in the
northern shores of Europe identical with  those  o!
Cape Cod.  The farther north we proceed, the more 
54
Prof. Agassiz's  Lectures.
species we find identical in both Continents, from
causes which I am now about to relate.
  There is a certain extent of land in which all an-
imals inthe different regions of Europe, Asia and
North America are  found to aeree.   In  America
they occur lower south than in Europe, where  we
have at the 70th degree of north latitude, the same
mean annual  temperature of 32 degrees Fahren-
heit, as in America in latitude 50 degrees—20 de
grees farther  south.
  'T'his is  the northern portion of  this continent,
and the corresponding portion of the Eastern Con-
tinent.  Witbin these boundaries [the dotted lines
in the upper part of the diagram] the animals are
identical; even the aquatic animals in the seas are
also  identical, and extend  farther south than the
land  animals.   For example, we  have the fishes of
Baffin's Bay extending along the shores of Norway,
Scotland and  Ireland  to  a lower latitude than that
in which the identical lat.d animal* in the Asiatic
and  American ice-field* are  found.  Indeed, we
have some of these  arctic fishes  coining as far
south a* Cape Cod, and occasionally still farther.—
There i* no identity  between the main portions of
the two continents, bnt  around the Pole  there is a
region where the  animals  of either verge of the
continents are identical.
   As *oon as we go farther South we  find in the
temperate zonea of Asia and America the animals
all become  distinct  from the  arctic  animals and
differ among themselves,  so much so that those
of the temperate  region of Europe  are distinct
from those in the same  region of North  America.
Still there is a great likeness between  them, so
great that  the first  settlers of this country  gave
them the names of European animals.  You  have
the fox, the bear, the deer and the  marten, which
are so many  names of European animals.  In fact
all the vulgar European names are applied to your
own animals. But notwithstanding this, the ani-
mals of the two continents are ouly analog ms, and
as specifically distinct  as  some allied species are
distinct  among themselves.  For example, two
species of foxes are found in Europe,—tbe common
fox, and the jackallon the shores of the Mediterra-
nean, differing in  the same manner  as  American
from European foxes, or as some in Central Ameri-
ca differ from those in this  region.  Thus you see
that as we  recede  from tbe cold climate of the
North we find animals  gradually becoming more
and more distinct, and showing  a certain analogy
which is very striking among certain types, though
less so in others.   I may go so far as to say that
the  genera are the same, though species differ.
   As soon  as we reach the tropical regions we have
not  even an  analogy between the genera. Animals
of Tropical America  and Tropical Africa  and South-
 ern  Asia differ materially.   We have no such ge-
nera as the hippopotamus, rhinoceros and elephant
in Central America,  nor do the tapir and llama ex-
ist in Africa. There is only the camel correspond-
ing to the llama in Tropical America  All those in
the  tropical regions of that  world have no analo-
 gous types in Central America.
   As  we recede to  the temperate regions of the
 South, we return to a greater similarity of type*.
 In the southern extremity of America we return,
 as it were, to the type* in tbe Arctic region*.  Bat
 the southern point of" Africa is peculiar and di*tinct
 in its animals, and the Continent of New-Holland is
 so exceedingly different from everything else that
 there is a combination of animals having no analogy
 with any other groups  in any other  spot  on the
 globe.  And indeed what is still  more curiona, is
 that the didelphides found in all parts of New-Hol-
 land occur often in New-Guinea, in those warmest
 portions of New Holland, and  also in the temperate
 regions, so that we have here a most striking evi-
 dence that these modifications of types are not ow-
 ing to temperature, but that they  are regulated by
 a higher design, one which escapes our observation,
 unless we refer it to the primitive  Law of all exist-
 ence.
   1 would not go beyond these few remark*, only
 to mention that even in the Pacific there are simi-
 lnr laws of distribution; and animals iu the northern
 portion are identical with  those on the  Asiatic and
 American shores—while in the temperate and trop-
 ical portion there is no analogy at all.
  Some marine groups of animals are circumscribed
 in narrow limits, though they are at liberty to swim
 in all directions.  There is  a group of  fishes com-
 mon in the Indian Ocean, very little known in this
 part of the world,  and not represented either in
 America. Europe or  Africa, but confined about the
 large islands between New-Holland and India Pro-
 per.   In this little group of islands there is a  family
 of fishes circumscribed  and not extending into the
 Pacific, nor even all over the Indian Ocean.
  This shows again howlimitedsome types can be,
 notwithstanding the power  they possess of travel-
 ing about in  all directions.  Far from considering
 this power of locomotion a reason for the spreading
 of animals, I think it is  only a cause for their keep-
ing within definite boundaries.  Being at liberty to
change their location they  will keep  within the
most congenial  boundaries,  and not be scattered at
 random.  That the eggs of fishes can be carried by
currents is true, but  we do not find  that  this  in-
fluence causes the fishes to be so diffused ; but, on
the contrary, they remain within what appear to be
their original boundaries.  In  fact,  we can come to
no other conclusion than that  they have originated
 where they exist.
  We have  another  fact connected  with  this
 which is  highly interesting,  and perhaps will
 throw some additional  light  upon the origin of
 Mankind.  The different varieties of men are cir-
 cumscribed in boundaries similar to those occupied
 by natural groups of  animals.   In other words, the
 different races of men cover the natural boundaries
 of the definite  associations in the Animal King-
 dom
 _ But, without going into details in this investiga-
 tion. I will proceed to elucidate the subject  of the
 Order of Succession of  Types in Geological epochs.
  It was necessary to  show that all animals are
 limited to certain natural  boundaries, which ap-
 pear to have been  their original location,  in order
 to show tbe importance of a knowledge of the char-
 acteristics of fossil animals.   If it was not tbe fact
 thu all fossil animals of New-Holland are identi-
 cal m type with those now living in the same lo-
 cality, and that the  fossil types of South America
 agree precisely in  type,  though  not in specie*,
 with those now living in Brazil, 1 would long since
 have left the subject.
   The subject of the order of succession of types in
 geological epochs, is one which  has been consid-
 ered by geologists in a different point of view from
 that in which I shall now consider it.  Perhap* it
 is proper for me to make a  few remark* upon 
The  Animal Kingdom.                               55
 the value  of investigations made under different
 view*.
  Geologists have for a long time known that fos-
 sil* in different strata are not the same.  All the
 species that have been found have for the most part
 been fully described,  figured,  and  well compared
 with living animals.  It has been shown that strata
 of different ages contain no identical  species.—
 Nevertheless all I have now to say has  been  men-
 tioned in works in which these facts are related.—
 Geologists have considered fossils by themselves—
 as medals  by which they can ascertain the ages of
 geological  strata. They have, in fact, been enabled
 by these fossils to find out whether certain strata
 of rocks are older than others.  What I have found
 on investigating the same subject, has  been, that
 the  order of that succession  corresponds precisely
 with the gradation of types of animals when clas-
 sified according to their structure. Zoologists have
 done an extensive work, in connection with anato-
 mists, in investigating the structure of animals, and
 from their external characters they have worked
 oat  a classification  more or  less natural, and a
 methodical distribution of them, forming  a  com-
 plete Zoological system.   These series of investi-
 gations  have been  traced for half a century  since
the  first researches of Cuvier, and his classification
 according to structure.
  Here, then, we have two series of independent
observations;—first, those of geologists, ascertain-
ing  that in different successive strata there are  fos-
sil*  of different kinds and species which do not oc-
cur  in other series of strata above or below ; and,
second,  the classification derived from the structure
of animals.
  What I can add is this;—to show that these two
series of phenomena cover each other:—that you
may read  the order of succession with a certain in-
telligence and you will find that the classification
according  to succession agrees precisely with  the
classification  made  according to the structure of
animals.
  In order to make  this evident, let me mention  a
few geological facts.   The  whole series of strata
forming the crust of our globe, not  to include  those
which contain no fossils, can  be divided into a se-
ries of layers, each of which contains certain fossils.
  The lowest strata, for in
Stance,  the  limestone,  s<
extensive over the northern
and western  parts of this
State, belong  to the oldest
formation deposited during the existence of animal
                      Jlife.    There  we  discover
                      (the oldest animals.  Above
                   fj^this we find another  set of
 $N<iNW»X^^W^V\\Wocks  which  are allied to
 \\^\W\^X^^\W|them. containing coal—stra-
                   " "Jta »o  extensive in certain
part* of the Middle States and in the West.   The
oldest  strata  of coal 1
would unite with the low-i
est  series  under the name]
of primary rocks.  Then
we have a series, not  ^-^/f///////////////////////,
tensively   developed in£r
this part of the  world, in
which the new  red sandstone of  the Connecticut
Valley forms a part, to which belongs the series of
oolitic rocks so extensive in the South of England,
and the bluish linien.i-.one of Somersetshire and  York-
shire, and above that the chalk. All  these have a
certain connection, and have been called secondary
strata. In thenetht-  green sands of New-Jersey  are
included.  Above that we have strata of a more re-
                            cent date, which con-
                            tain shells similar to
                            those  now  in  exist-
                            ence ;  th«-se  strata
                            are  called  tertiary
                            beds.  The primary,
                             econdary  and  tertia-
                            ry beds are not to be
                            mistaken  for  those
                            rocks which have no
                            stratification and con-
                            tain no fossils.
                              Let me  mention
that fossils found in the primary beds, and even in
the different layers of the primary beds, are differ-
ent from one another, as well as from those found in
the secondary beds.  Geologists have known this
for half a century.  Again, the tertiary contain fos-
sils entirely different from the  secondary.   I will
represent these layers by conctntr c circles,  which
will be in accordance  with the forn of  the  earth,
only the proportions will notl
be  true.   Let this  be the!
most  ancient strata  formeol
on  the  primitive  rock;  the*
next,  the secondary ; and the!
upper,  the  tertiary.  Thest-I
strata have been distributed!
in an  irregular manner,  some!
being inclined by the upheavT
ing of tbe Plutonic or volca-
nic masses, which have modified their primitive
horizontal position.  But all  these details belong to
Geology, and have no connection with tbe order of
succession.
   Now  there has been an opinion prevailing among
geologists and naturalist?,  that  the animal* suc-
ceed  in  these different  strata in  an order corres-
ponding to their zoological  gradation.   The view
has been widely entertained, and it is still the
opinion of many philosopher*, that the higher types
were gradually introduced,  until  at last Man was
formed.
   This view, thus expressed, is entirely false;  in-
vestigations of geologists having shown, to the con-
trary, that in the most ancient strata there are pol-
yps,  echinoderms, and in the Trenton limestone
even  higher types of the most ancient echinoderms.
There are also bivalve shells, cephalopoda and
Crustacea, found  in the most ancient  rock*;  and
there are also fishes.  We have, therefore, not the
lowest  types in  the  oldest strata, but  we have
representatives of all the types.  After this fact
had been ascertained, geologists were led to be-
lieve that there was no regular order of succession
in  the  appearance of fossil*.  We have gastero-
poda—all classes of molluscs, acephala and cepha-
lopoda, we have trilobites  belonging to tbe order
of Crustacea;  and we have  some shells  similar to
those of worms, which have induced geologists to
consider the class of worms  as belonging to the old-
est strata; and we have fishes.  Therefore the no-
tion of succession in constant, regular order was de-
nied,  and it is this view which generally prevails
among  modern geologists and naturalists.  After
they  had been under the impression that types in
the order of succession correspond to the gradation
of the Animal Kingdom, beginning with polypi and
ending  with the class of fishes, having found  fossil*
of all the  different classes in the lowest  beds, they
actually denied all order and  every  evidence of
plan in the succession of types.

   Now let os  investigate and ascertain  what oc-
curs in the oldest strata. What animals do we
there find 7  That is the question for examination.
I 
56
Prof.  Agassiz's  Lectures.
In this diagram I have divided the circle by draw-
   A..Primary.      B..Secondary.    C. .Tertiary.
No. 1.Mammals.  No. 5.Cephalopoda No.10.Worms.
 .. 2.Birds.     .. 6.Crustacea.   .. 11 Polypi.
 .. 3.Fishes.     .. 7.Gasteropoda.  .. 12.Echinoderma.
 .. 4.Reptiles.   .. 8.Insects.      .. lS.Meduse.
               .. S.Acephala.
ing four heavy lines from the centre,  making  four
sections.  In these sections I  have drawn lighter
lines radiating from the centre, to indicate the or-
der of introduction of  the  different classes.   We
have in the  primary strata vertebrated animals, as
is indicated  by the light lines extending  into the
primary strata.  1 n the most ancient strata we find
fishes, but no reptiles.   The type of reptiles is not
found till after the coal era.   The section on  the
right side contain* the class of molluscs.  You re-
member  1 divided this  type  into three  classes:
acephala, gasteropoda  and cephalopoda.  These
three classes occur at once in  the beginning.   We
have bivalves under the form  of spirifers and tere-
bratula; we have gasteropoda in the form of univalve
shells, and we have cephalopoda.  So we have three
classes of mollusc*, but only one of vertebrated ani-
mals—tbe fishes.  In the left section I have figured
articulated  animals.   We have Crustacea  from the
beginning.  We have insects in the coal, which be
longs to the primary beds ; and we have worms in
the most ancient strata.  So we bare in the prim
ary epoch the three classes of Articulata.  In the
bottom section I have figured  tbe  classes of Radi-
ata.  Now we have the polypi from the beginning.
and also the echinoderms.  The soft  animals,  the
medusae, are not found in ancient strata, but in the
oolitic series ; also in the lithographic limestone of
Germany impressionsofjelly-fisheshave been seen.
There is no doubt, then, that if this class existed in
the oolitic epoch, they existed earlier; only on ac-
count of their softness tbey havenotbeen preserved.
So it is likely that three classes of radiated animals
existed,  and  we  know that  two—the corals and
echinoderms—were numerous.
   So we have the nine classes of in vertebrated ani-
mals beginning in the lowest stata,butonly one class
of vertebrated animals—the fishes—in that epoch.
From the beginning, therefore, animals of all class
es, except the three higher classes of vertebrated
animals, were at the same time called into exist-
ence—even all classes of invertebrated animals,
and fishes among vertebrated.
   But now let us  examine what we have in these
different classes in the geological epochs.  I will
take a few  examples  in order  to give an idea of
the order of succession.  Having made Echino-
derms a  particular study, I can give more precise
examples from them.  All  the  ancient type* are
crinoids.   You  remember that the class of echino-
derms is divided into three orders—polyps, echini,
have stems there is only one species now existing
—the pentacrinites, and what is singular is that our
free star-fish, at least the family of ci matula, have
snch astern in their young *t ate, and the youngbear
a strong resemblance to these ancient types.   Tbe
next family which succeeds these is the free-star- 
The  Animal Kingdom.
57
fish.  Thus we see that class branching into differ-
ent families, and these divisions also correspond to
the types which begin to exist in different epochs.
  I said we have no free echinoderms before the
secondary strata. Now free star-fish of a higher or-
der begin to exist  in the  tertiary formation, and
the multiplication of types is accompanied with a
gradual extinction of the primitive fixed star-fish
with articulated stems. As the forms become more
free  and  more different among themselves, the
primitive stock is less numerous, until at the pres-
ent time only one species remains.
  Of the  polypi I cannot explain the order of suc-
cession, though the living  ones have been beauti-
fully illustrated.  Tbe forms of the  fossils have not
been compared to show any relation to the living
■pecies.  There is yet a wide field for investiga-
tion in  reference to the gradation  of  structure in
living ones and the order of succession of ancient
types.
  Among the molluscs I could point to very similar
facts.  Tbe class of bivalve shells, to which I have
already alluded, is represented in the  oldest strata
only  by such irregular bivalves as the brachiopoda.
There  are  no regular bi
valves in the primary strata ;|
it  is only in the secondary
that we find them, and only
in the  tertiary do we  find
that variety of shells  exist
ing now.   But wehaveseeii!
that  the  gradation  in the;
class  of acephala  is sue!
that the brachiopoda should'
be considered the lowest.
  The Monomyaria next succeed; then those which
have two muscles.   In that class we have an agree-
ment between the order of succession of types
with geological times, and the order when classified
by their structure. The same fact can be seen in the
cepholopoda.   Those allied to  the nautilus—the
gonoidoe—are  the lowest,  while the  naked types
are found in secondary strata.
  Among Crustacea, the lowest are tbelj
trilobites.  Who would consider themp
as higher than the lobster or crab ?—
They are similar to the larvm of crabs
Any one who has investigated the firi-tj
formation in the egg of the young crab
                    Iwill   remembei
                      ine form  within
                     the egg which  shows  only
                     such transverse  divisions,and
                    levt n atthe beginningwe see a
                    Ikind of depression from which
                    Iche  successive  rings   will
                    lsend forth respiratory organs
                      >r external   appendages.—
                  ^JlJut  seen from above they
       ,c hIidul this t.irtu, with perhaps some ap-
pendage here which is wanting  among
trilobites.  There is such a close resem
blance between young crabs  and those
ancient  trilobites—the  only Crustacea
found in  the primary beds—that  it is
quitf extraordinary that the old agref
with the  first form  of young Crustacea
in the egg.
  Next  we have  the  lobster tribe—
which  occur  in the secondary  strata.
We know that crabs stand higher than  the lob
■ter, and there are  less  of these  external ap-
pendages in the tail of  crabs—which  append-
age*   are  by no  means  indicative of  superi-
ority •  therefore wo consider  the  crab  as higher
than the  lobster.  But the crab* begin to appear in
                       5*
the chalk jnst after the existence of the long-tailed
crnstacea.
  So we have given tbe order of snecesaion of these
types agreeing with the gradation of form  now in
existence, when we consider only  their organiza-
tion.  I could mention  tbe first appearance of the
wingless insects, with a form allied to that of the
spider and tbe scorpion tribes,—the only ones are
found in tbe coal deposition;  those with wings,
analogous to the more  perfect insects, beginning
and occurring in the secondary strata, in the beds
of chalk and the oolitic series.
  So we have in all classes the  lowest existing
first,  and of invertebrated animals all classes in
existence at once, because worms have been found
from  tbe  beginning.   So  there can be no doubt
that if all classes began to exist  simultaneously,
their lowest types occurred first, and their higher
types appearing in succession—a great variety be-
ing established only during the existence of Man.
   What are the  facts with vertebrated animals ?
We find  fishes only in  the older strata.  In the
secondary strata reptiles prevail considerably, with
some indication of birds, and at very late epochs
another indication of mammalia.  But in the terti-
ary beds  we find reptiles, birds,  mammalia and
fishes, animals which illustrate  all  the types of for-
mer epochs.  But do we find  tbe  first fish called
into existence to be the lowest 1  By no means.—
The types of those first created must be considered
the highest in their class.  The first class that ex-
isted are the ganoids—those covered with enameled
scales,  in which wa see some likeness  to reptiles,
and in  fact indicative of higher orders which were
not existing at that time.
   Then again at another epoch—when reptiles be-
gan to exist in the secondary strata—we do not find
batrachians first, but reptiles allied to tbe crocodile
—the Rhizodonts—which indicate, by their charac-
ter and form, a likeness to  Mammalia, which were
called into existence later.  There is  a great re-
semblance between these and cetacians—so great
that in some respects it is difficult to distinguish their
bones from cetacians.
   Again, we find pterodactyl'es, as allied to birds,
which were called into existence later.
   So we see that the first types of the oldest verte-
brated classes which are introduced are the highest
among themselves.  They are prophetic types, in-
dicating the future existence of other types at a
later epoch, and if we trace all these series we can
go so far as to  see that the order of succession ia
such that there is only one chain in  the whole series
of  vertebrated animals, indicating from tbe begin-
ning  an intention to introduce at last Man,  the
highest type, at the bead of Creation.
   And this point of view allows us to consider tbe
vertebrated animals aj the only one in which there
is a progression of this peculiar kind, in which the
first step  is  already indicative of another higher
step, till the complete aeries is accomplished.
   it would take me much beyond the limits of my
time if I were to enter into the details of all these
types.  Let me only show  that these  types suc-
ceeded each other in such a manner that they can-
not be considered as derived from each other. They
may be considered as entirely independent of each
other and only connected, in the idea of the Creator,
in the same manner sb  tbese facts, of which we
showed a succession, are connected, not materially,
but in our minds only. All these fishes, though they
have analogy to reptiles,  are nevertheless by their
characters true fishe* : they have fins, gills, a verte-
bral column, and articulated fingers in tbe form  of
singularly modified fins with numerous ray*.  Even
in different strata of the primary roeks we find fishes
of  different genera and specie*.  We find  in the 
58
Prof. Agassiz's  Lectures.
secondary strata again other fishes—and,  what is
singular, tbe moment the class of reptiles begin to
exist, these fishes no longer show so strong a like-
ness to reptiles, but begin to resemble  more  the
fishes of our own day.   In the cretaceous series we
have all the types now in  existence, though  tbe
genera with bony spine, dentated scales and multi-
plied fins on tbe back, show no indication of exist-
ence in the ancient strata.       n
  But reptiles which first exist, assume all thechar-
acters we find in the beginning among fishes.  But
can they be considered as derived from those fishes ?
No more than any of our living species can be de-
rived from another.  There has  never been a spe-
cies derived from another.   We have always seen
the order of reproduction remain within  tbe  natu-
ral limits of the species, and it never passes from
one to another. It must be maintained as a natu-
ral law that one species will not produce another,
for what does not take place now cannot  he admit-
ted to have taken place in other epochs.  If it had
been so, we should find intermediate  forms, and in
such a manner that they could be shown to have
been derived from  different species  existing pre-
viously.  In fact, the anatomical characters in rep-
tiles are such that  there must have been a change
in structure, and such change is never assumed ex-
cept in  varieties which cau be  found in tribes of
domesticated animals when the  races are mixed.
These effects are entirely different, from those of a
succession of different species in geological epochs.
So we would consider this analogy  between the
ancient fishes and the  reptiles of a later period—
this  change of character in fishes when the rep-
tiles begin to exist, and then the renewed changes
in the successive ep'ichs as indicating merely that
at such epochs thr plan contemplated at the begin-
ning has actually been effected, and  these modifi-
cations, which were intended to  carry on the pro-
gress up  to  the  appearance of Man. have  been
gradually accomplished by the Creator.
  There is, therefore,  in this  view a gradation  in
all vertebrated animals   There  is no such in tbe
invertebrated:—they were intended to be compan-
ions of the vertebrated  throughout the geological
epochs, improving till they acquired that great va-
riety which now accompanies Man—which type of
vertebrated animals was intended to be the  stock
from which the highest type should spring forth at
the latest epoch, then to find all that variety in the
lowest animals. Therefore we conclnde tliHt Man is
not only the  highest group in Creation, but is the
last intended type.  We can even  go farther, and
say that this having been the intention of the Crea-
tor from the beginning, we can expect no higher
progress or new development.  The creation of
Man is the highest possible development in  the
progress of Creation.
  In this view we are borne out by other  fact*.
For though the different geological type* have been
introduced upon different point* of the surface of
our globe—and though, as I  have stated,  animal*
in different parts  of the globe  are  constantly  cir-
cumscribed—Man at last began to be diffused, and
to acquire a power  over Nature which no  other
species ever had. At  no epoch  has  any  species
ever had such a marked superiority over another a*
Man has now over the lower creation.
  Again, when in any point of view  we compare
the structure of Man, we can see that he  was the
last object  intended.   You  remember that  fishe*
have a brain very little larger than the spinal mar-
row and it is placed horizontally with the vertebral
column: the class of reptiles begins  to raise its
head : in th<? class of birds the bead rises still high-
er : but in  Man a position is assumed to which there
is no superior.   He stands erect—with a large brain
and a head of such a  spherical  form  thnt there i*
no improvement possible—but the highest degree
of perfection is realized on that plan.  Then if we
take in connection with this the fact that, in the
succeesion of types, the different species of animal*
are confined to particular localities,  and that Man is
spread all over the surface of the earth, we have an
unmistakable  indication  that Man  was  not only
the last creation up to the present time, but was in-
tended to be the last—and that no material progress
is possible on that plan, but all progress to be ex-
pected within  the limits of Mankind is  improve-
ment in intelligence and morals.  [Great applause.]
  Professor Agassiz here reached the conclusion of his Coarse, amid the general applause of a highly
attentive and intelligent assembly—who, during the whole series of the Lectures, had evinced an intense
interest in the multiplied subjects  so ably yet succinctly treated.  Professor A. retired from our mid*t
accompanied by the warmest congratulations and sincere hopes for future success of a multitude of our
most distinguished and talented citizens. 
    HYDRAULICS   AND   MECHANICS.

A Descriptive and Historical Account of Hydraulic and other Machines for
  raising Water, ancient and modem;  with observations on various subjects
  connected  with  the Mechanic  Arts,  including  the Progressive Develop-
  ment of the Steam-Engine.   Descriptions of every variety of Bellows, Pis-
  ton, and  Rotary Pumps,  Fire-Engines, Water-Rams, Pressure-Engines,
  Air-Machines, Eolipiles, &c.   Remarks on  Ancient  Wells, Air-Beds, Cog-
  wheels,  Blowpipes, Bellows  of various People, Magic Goblets,  Steam
  Idols, and other Machinery of Ancient Temples.  To  which  are added
  Experiments  on Blowing and Spouting Tubes, and other original Devices.
  Nature's  Modes and Machinery for raising Water.   Historical Notices
  respecting Siphons, Fountains, Water  Organs, Clepsydrae,  Pipes, Valves,
   Cocks, &c.  In  Five Books.

                    BY  THOMAS   EWBANK.

         ILLUSTRATED  BY  300  ENGRAVINGS.
  This volume, on the various machinery connected with the raising of water, is a very interesting
production ; not only to the Experimental Philosopher, the Mechanician, and the Operative Trades-
man, who are engaged in the  researches and work combined with the objects  specified in the
Treatise, but also  to  every ordinary reader who is solicitous  to enlarge  his general informa-
tion, and who wishes to combine amusement with the topics which attract his attention.
  It is impossible in this concise notice, to  detail a minute syllabus of a book, the mere topical
index of the contents of which occupies nearly eight pages, numbering about one thousand dis-
tinct articles ; but a general view is presented, from which the nature and value of the disser-
tation can easily and correctly  be estimated.
  The first book, which is subdivided into eighteen chapters, comprises a narrative of the various
" Primitive and Ancient Devices for Raising Water," which are exemplified by sixty-seven en-
graved  specimens of their diversified contrivances.  This is  not merely a dry philosophical
comment, for there  are many episodes commingled with it of  a peculiarly interesting charac-
ter, of  which the preliminary remarks on  the historical accounts of warriors,  and  the section
in chapter sixteen, on the " Flattery of Despots by Men of Science," may distinctly be mentioned.
  The second book, which includes seven chapters, describes the " Machines for Raising Water by
the Pressure of the Atmosphere."  With this part are incorporated thirty engravings, delineating
the chief inventions  which have been used in that department.
   The  third book, containing nine chapters, develops the " Mechanics for Raising Water by
Compressure, independently of Atmospheric Influence," with sixty-nine pictorial representations
of bellows,  pumps,  and fire-engines.  The  discussions respecting water-works  ana  fire-engines
are full of instruction, and combine more information upon those important topics than can be
found, it is believed, in any other work that ever has been published.
  The fourth book is extended to nine chapters, and displays the " Machines for Raising Wa-
ter, chiefly of Modern Origin, including Early Applications of Steam for that Purpose,'' with
thirty-one  engravings. This portion of the volume is very racy, especially the details concern-
ing the Altars and  Heron's Spiritalia, with the introductory paragraphs to chapter three, from
page 381  to 391, and the notice of the Eolipilic  Idols.
  The fifth book, which also  comprises nine chapters, with eighty-four engravings,  unfolds the
" Novel Devices for Raising Water, with an Account of Siphons, Cocks, Valves, Clepsydrae,"
&c.,the seventh  chapter of which, on Fountains, condenses a large quantum of information upon
that cooling and refreshing topic, which is followed by an attractive elucidation of hydraulic
organs.
  An Appendix, with five engravings, supplies some additional explanatory facts ;  and to the
whole is subjoined a comprehensive index of all the principal  subjects that are embodied in
those pages.

   In addition to the above, the present  edition contains  a Supplement of over
thirty piig«'s,  on ANCIENT EOLIPILES, with some curious illustrations.
   The entire work, witli an Illustrated  Titlepage, will cost but half the price-
of the previous  editions.

   \^F The above work is now publishing in EIGHT PARTS or numbers,.
at 25  cents  each.           GREELEY  & McELRATH, Publishers,
                                             Tribune Buildings, New York. 
EWBANK'S   HYDRAULICS   AND   MECHANICS.
                                 OPINIONS OF THE  PRESS.

  This is a highly valuable production, replete with novelty and interest, and adapted to gratify equally the his
torian, the philosopher, and the mechanician, being the result of a protracted and extensive research anion« the
arcana of historical and  scientific literature.  Mr. Ewbank's work can not be too widely circulated.  It U  an
elegant " Tabte-Book," suitable to all persons—to the  ordinary reader, who is anxious to acquire useful knowl-
edge, as well as to the theoretical and practical  connoisseur in hydraulics.  Hundreds of impressive hiogrnphi-
eal and historical anecdotes, generally unknown, might be quoted as proofs of the multifarious intelligence  which
Mr. Ewbank has amassed for the edification of those who may study his richly-entertaining volume. We know
not a compilation specifically desi-med to exhibit that mechanical philosophy which appertains to common, do-
mestic, and social life, with the public weal, to which the attention of youth can be directed with equal amuse-
ment and beneficial illumination as  to  Mr. Ewbank's  acceptable disquisitions.  Therefore we earnestly recom-
mend his volume to their study in preference to the perusal  of  those  fantastic and pernicious  fictions  which
pervert the imagination, and deteriorate the  mind, and corrupt  the morals of the thoughtless myriads who
-'feed on those ashes."—National Intelligencer.
  It throws more light upon the progress of mankind from the earliest ages, in the useful arts, than any volume
we have ever seen.—Alexander's Messenger.                                                .
  The onlv volume ever published embracing an account of all the contrivances employed in different ages by
different people for raising water.   It. is really one of the most remarkable  publications connected with me-
chanical philosophy that has ever fallen under our observation.—Merchants' Magazine.
  We have Ion? known that Mr. Ewbank was preparing this work for the press, and have looked for its publi-
cation with a conviction that we should derive much valuable information from its perusal; an expectation that
has been fully justified by the result.  His work is not one which can fall still-born from the press, as it is not
one of those ephemeral productions that must sell at the moment or never.—Journal of the Franklin Institute.
  An interesting work of. science.   The title will furnish  the reader a good general notion of the matter of the
book, but not of the clearness,  method, precision, and ease of the manner of it.  We believe there is no work
extant which treats of the specific topics which he  has  chosen—none we are certain which describes  it with
more fullness of argument and illustration.—Democratic Review.
  All classes, as well the farmer and professional man as the artist and engineer, will rise from a careful peru-
sal of Mr. Ewbank's book wiser and better.—  U. S. Monthly  Review.
  It contains more valuable, curious, and interesting information  than can be  found in any volume ever pub-
lished on the subject, and is a work which commands the attention, and should be placed upon  the shelf, of
every gentleman's library, and in every college and academy.—N. Y. Sun.
  A splendid book.  We nre inclined to believe that it will be one of the most curious and interesting works that
have issued from the American press for many years.—N. Y. Tribune.
  It po6seFses great interest, not only for mechanicians, engineers, and men of science, but for intelligent read-
ers generally.—Philadelphia Enquirer <$■ National Gazette.
  A rich mine for exploration  by the  practical or theoretical engineer, as well as by those who like to make
themselves acquainted with the developments of mechanical ingenuity.—N. Y. Commercial Advertiser.
  This large and beautifully-printed octavo is probably the most  valuable volume that the publishers have pre-
sented to the public during the past year.—N. Y. Courier if Enquirer.
  It is a scientific work, but commends itself not to the scholar only, but to the mechanic and general  reader,
for it is perfectly free from pedantry and learned affectation.—Boston Daily Times.
  An Encyclopedia of mechanics.  It is richly illustrated, full of curious information,  and every way worthy,
by its copious  knowledge and its  incentives to curiosity, not  only to a place in every gentleman's library,  but
what is more, to one on the shelves of every  district school library in the state.— Union.
  A thick volume of nearly 600 pages; but let  no reader be dismayed by its size, for the author says with a
good deal of truth, that in" the annals of mechanics are to be found incidents as agreeable and exciting in their
nature as anything that can be realized by the imagination.  We  are not sure that a  single corner of the world,
or recess of history, has escaped his laborious researches.—JV. Y. Evening Post.
  Whoever rejects this book from the supposition that it is a dull detail of machinery and the various applica-
tions of the mechanic powers, will be  guilty of great injustice to  the author.  It is one of the most entertaining
books we have ever met with, on a scientific subject.  It is full of interesting historical and well-written de-
scriptive matter, interspersed with appropriate quotations from old writers, enough  almost to give it the title of
The  Poetry  of Mechanics.—Boston Courier.
   One of the most valuable scientific works which this country has produced.—Albany  Advertiser.
   "t entitles him (the author) to take  rank at once  with the very best writers in this department of literature.
i,  ether ancient or modern.  Quite as entertaining as Beckman, he exceeds him immeasurably in practical  use-
fulness ; and while aiming, like Ferrruson, at a popular style, he brings  to his aid a liveliness of fancy, depth of
feeling, and eloquence of  expression,  to which Ferguson was  a  stranger.  We have seldom seen a volume so
absolutely ciammed with useful information.—London Mechanics' Magazine.
   A compressed library.  On the subject here treated, tomes have been multiplied to an amazing extent. Their
essence is given in this volume.  In short, it is such  a work of labor and original research as we rarely see. It
is an acceptable contribution to the literature of mechanical science and practical  engineering.  It is the kind
 of book which every mechanic or inventor ought to consult.— London  Athenaum.
   This work is eminently entitled to be called a history of the human race, since it carries us forward from one
 stage of advancing civilization, beginning with the rudest and most simple  efforts  of ingenuity, to the almost
 immeasurably superior wonders of our own day. . . . Whether viewed as a purely philosophical work, or  as a
 comprehensive text book for mechanics and inventors, Mr. Ewbank's book is equally valuable.  The mass of in-
 formation it contains is unusually  great, and the immense variety of machines which it describes are illustrated
 with about 300 engravings.  It is capable of saving infinite trouble and mortification to inventors. . .. We  have
 seldom seen a more instructive and amusing work.—From the Surveyor, Engineer, and Architect's Journal.
   This work exhibits the results of reading and research seldom manifested in these days of book-making.. .
 Description, however, unless  as copious as an index, would fail to afford an idea of its extent and value.—Lon-
 don Literary Gazette.

    E7*  The above valuable work is now publishing  in EIGHT PARTS, and sold at 25 Cents each-

                                      GREELEY & McELRATH, Tribune Buildings, Publishers. 
Prl«« : In Paper Covers, 37i cts., In Boardi, neatly bound, 62* ot*.
                  A TREATISE  OX  MILCH  COWS,
Whereby the quality  and quantity of Milk which any Cow will give may be  accurately deter-
   mined, by observing Natural  Marks or External  Indications alone  ;  the length of time she
   will continue to give Milk, *•*  kc.   By M. Francis  Guenon, of Libourne, France.   Trans-
   lated  for The Farmers' Library, by N. P. Trist, Esq.  with Introductory Remarks and Obser-
   vations on THE  COW AND  Th^ DAIRY, by J.  S.  Skinner, Editor of The Farmers' Library.
   Illustrated with  numerous Engravings.
  |ty Price for single copies, neatly done up in paper
covers, 37* cents.  Library edition, full bound in cloth
and lettered, tW£ cents.  The usual discount to Book-
sellers, Agents, Country Merchants, and Peddlers.
  This extraordinary Book has  excited the attention
of the ablest agriculturists of  the  country.  Five
Thousand copies  were sold in  the first four weeks
of its publication in New-York.  The Publishers have
received numerous testimonials  as to the usefulness
and accuracy of Guenon's Theory, while othen, from
partial experiments, have doubted its  accuracy.  The
practical remarks, and the useful  information  con-
tained in the first part of the  Book  are worth more
to any Farmer than the whole cost.
  Since the days of Doctor Jenner's discovery of vac-
cination, or the Cow-pox, being an nntiilote in ! ke small-
pox, nothing has  appeared  so  extraordinary  in that
department ot' natural history  as the discovery by M.
Guenon,  the son of a French gardener, of a means of
ascertaining the quality of Mitch  Cows  by external
and visib'e signs over the milk region  of the animal.
  The signs have been  reduced to a clear system, and
by committees  of various agricultural societies  in
France pronounced " infallible,"  after repeated and
most careful trials.
  The work was translated by Mr. Trist of the State
Department, and published with numerous engravings,
explanatory  of the system, first in The Farmers' Li-
brary.  But the publishers, not willing to withhold a
discovery so important and valuable from the  poorest
person owning, or wishing to  own, a Cow, have pub-
lished it in a separate  and  cheap  form, and it may be
had at The Tribune  office, or  at  most of the cheap
publication offices in the U'ited States.
  While those who have given to this work even the
slightest tests aver thut, with it for their guide, they
are not fearful of ever again buying an indifferent
Cow; others who have been more minute and careful
in applying  the " signs"  to living animals, declare,
like  the  French  agricultural  committees, that the
marks are obvious and worthy of every reliance.
  The following, from sources  of  unquestionable ve-
racity  and  practical  knowledge, are  submitted  in
proof of the  truth of this wonderful discovery.  But,
independently of  the great value of the Cow-book for
the purpose  in  question, other matters attached to it
will fully recompense the purchaser for the trifling cost
of the hook itself, which is but 37£ cents.   Booksellers
and publishers may be supplied at the usual discount.
   Under the operation of  this  system, which  enables
every one to s»lect and   put  aside for  the butcher
calvec that will  be sure  to prove bad  milkers, the
7i'/io(e race of milch cattle  may  be rapidly improved
through.nit  the Union.  Every  great discovery ap-
peals iu lit- strange, and some of  them incredible in
the lirst instance, and few more  than vaccination it-
self
   We find in the Boston  Traveller an  account of the
proceedings of an Agricultural  meeting, lately held
in the Legislative Hall,  in Boston,  from which we
make the following extracts:
   M.. Ilrooks made dome  remarks on  the ability of any one to
learn to distinguish the .jiialit i.s of a Cow by examination.  He
had n vers hc-h opinion of a French work, liv C.u'.n n, recently
 niihli WinTlie Farmer.-' I.ibran , by Mr. &iii»rr,ol'New-York.
 IU tin- aid of that work, a man might select In* stock with almotl
\nhillible cmaituy.  He believed lie  could tell, within a few
quarts, what  a o<w would  yield  of  milk,  and within a few
pounds, what situ would yieltf of butter.  Hi- had not misted in
more than Ml inrancrt out qf between 300 and 400 trials.  He
had known one Cow that was* not dry for fourteen years, and had
calves  every year.
   Mi  Dennu fully nccorjed with Mr. Brooks in bin e. timate of
the Treatise on Can!,-. by f.'ncwm.   He bad tested its value by
distributing u number of copies among intelligent, practical farm-
ers ;  and their united report was in favor of the lujsh value of the
work   One of thrill went so far as to any that a farmer keeping
.1,1 row* could well afford to give $100 for this Treatise of Gue-
non, fit <  nUd not be obtained at a less ci.'l.
  Mr  I'renrn eKpr^e.-wH hie »niir« «^'«m in t;u6iM»»'* r|lJ**
t■•.-,.  nnd thought its introduction among our farmers was dos-
  ed to wrk an entire revolution.   He mentioned the dim- ul
    which  ti'.Cnott i n-onni^red in getting hiework into notice in
p linen  For some time, none of the Agricultural Societies would
■n%e aiiv heed to In- suggestions: but when. »t length, one of
u„ n w n induced t> »"i  <••<<"'»' '" the test, they were perfectly
■Mii'inshr   ■  :hc ».  .....cy w t!i winch  be applied bib rules for
J«wruvi »,, ■■■'■  , \ gmue qualm-, of a C«»
  We have received  quite a number of letters from
different parts of the country, fully corroborating tha
theory of M. Guenon.  We select for publication tha
following:
                       Princeton, Mats. October Id, 1 S4o\
  Dear Sir: I received vour favor of the 6th m-t. denn^ me to
state my opinion of the value of M. Gui-irm's Treatise '°i Mitch
Cows, translated Irnm the French. i„,d pubb.-hed  in The Farmers'
Library. On my first meeting with tin- Treatise I was impressed
with its value,  from my  previous knowledge of -ome general
marks whereby tbe milking properties of Cows may.  in soma
measure, be determined, and from the fact that  1 had myself no-
ticed the oval maris above tbe hind teats, mentioned by M. Gue-
non as indicating good milking qualities, that 1 immediately com-
m need the study  and application of bis method to every Cow
that came under my observation. 1 have examined more than
one hundred Cows, and after carefully marking their escutcheons,
I have  become satisfied that M.  Guenon's discovery is one of
great merit, and can be  relied upon as true.  1 have no doubt
that I can judge very n■• irly as to the quantity and quality of the
milk any Cow will £ ve at the higbtofher flow, and also the time
-he will continue in in Ik alter being with calf.
  The way taken to convince mysefiof the truth of M. Guenon's
method has been to visit the cow-yards of some of our principal
dairy fanners, and examine the escutcheons  and marks on their
Cow., and make up my judgment  as to the quantity and quality
of unlk each Cow would give at the hight of her flow . .uid how
Ion;' she would continue in milk after being with ciili .  then in-
rpnre of the owners how much milk their several l "w, would
civ,- at tie- Inght of tbeirflow, and how long they would  holdout
alter being with calf: comparing tbe owner's account with  my
own judgment.  1 find 1 have mistaken in only five cases, out of
more than one hundred examined
  1 have great confidence  in M. Guenon'B method of testing  the
milking properties of Cows, and consider it one of the great dia
coveries of the age.  The advantage of this discovery to our dairy-
farmers, enabling them, as 1 think  it does, to determine the milk-
ing properties of their young stock at an early age, must be very
  Sreat, and wdl be appreciated by every one who is in the slighteat
  egree  acquainted  with the subject.  In my opinion, no  aairy-
farmer, after acquainting himself with  M. Guenon's discovery,
need possess himself of a bad milking Cow.
  M. Guenon informs us that his system is applicable to calvea
three or four months old.  I have traced the escutcheons upon
calves as early as two or three weeks old, and 1 see no reaaon
why their value  as future milkers may not be judged of at thtj
age as well as at any other age.      Yours respectfully.
  To J  S. Skinner, Esq.                 .loHN BROOKS.
       Kditor of The Farmers'Library, New} ..rk City.

                       Patersnn, N.J. December 19, lMo\
  Dear Sir: I have read, with r,reat satisfaction, M. Git,'k-hi'i
work on Milch Cows, by winch one can jud^-e by certain infallible
signs the milking qualities of the annual. I have compared  the
marks he gives for his first-grade Fl.ciders Cow, and fnui they
correspond with the escutcheon of my lavor.te Devon CoxoF.'Un
that has taken the first premium at the last two cattle shows of
the American Institute. My farmer has great faith in M. Guenon's
work, and so has one of my neighbors, aknowing Scotch milkman,
who keeps  fifty Cows.  He says that after careful examination
be places confidence in these marks, and tbey wdl govern bim ia
bis future purchases.
  1 return you  my sincere thanks for giving to ns fanners tiu
valuable Treatise of M. Guenon.  I shall hereafter make my se-
lection of the calves I will raise from my choice stocks from Uw
marks given by this author.  I think every farmer  should own
this work.              With regard, yours. &c.
                                 ROSYVELL  L. COLT.
To the Editor of The Farmers' Library.

                 East trmdsor Hilt, Ct. December 9, wv
  Dear Sir- Having had some experience in raising rows, aad
having h:nl my attention particularly called to their nidkin_;prop
erties, I was pleased to find a Treatise on the subject In  M. (iue
non, of Libourne,  in France—published by  you a  lew months
since, which 1 procured and carefully  studied.  And 1 think the
book more worthy of attention than I behave it has  received
from the public in this quarter
  1 have found that Ins escutcheons, or marks of the particular
classes und orders of Cows, to  agree with nearly all 1 have had
an opportunity to examine. It has been easy to ascertain, after
studying this book, to which class and order almost every (Yw
belungs, winch as a guide in purchasing Milch Cows, or (.1 'safely
deciding which to keep, before we have had time or opportunity
to test their qualities as milkers, will far more than repay the |ir>e
of the  book, and the time necessary  to a clear under-t oidni^
of it.       1 am. Sir. very' resu'y.your obe't servant.
                                  .TESSE  CHARITON.
To John .v. Skinner, Esq.  Editor Farmers,' Library.


  Country Merchant* visiting  any of the Citie   can
procu 1 r the Work from Booksellers for those who may
wish to obtain  it.  Please send on your orders. Ad-
dreu             GREELEY &  McELRATH,
         P  blithers, Tribune Buildings, New-Tort 
                               POPULAR  LECTURES


                    SCIENCE     AND     ART,
             DELIVERED IN THE CHIEF CITIES AND TOWNS IN THE UNITED STATES,

                        BY DIONYSIUS  LARDNER,
Doctor of Civil Law, Fellow of the Royal Societies of London an-1  Edinburgh, Member of the Universities of Cambridge
        and Dublin, and Professor of Natural Philosophy and Astronomy in the University of London, 4c. Sic
  After Dr. Lardnerhad brought to a close his Public Lectures in the United States, he was prevailed
upon by the Publishers to prepare a complete and authentic edition for publication.  The general in
terest which, for a period of several years, these beautiful expositions and commentaries on the Natu-
ral Sciences had excited, and which  was so universally felt and acknowledged, induced the Publishers
to believe that their publication would be most  acceptable, as well  as  permanently beneficial, to the
American public. In these  published Lectures it will  be found that the Author has preserved the
same simplicity  of language, perspicuity of reasoning, and felicity of illustration, whichrendered the
oral discourses so universally popular.
  The above work was  originally  published in Fourteen Numbers or  Parts, and sold at 25 cents per
number.  Any of the numbers can still be purchased. The entire work  is now completed in two large
octavo voluiies of about 600 pages each, well bound in full cloth, illustrated by 380 Engravings, and
sold at $4 50.
  District School Libraries can order these Lectures through any of the  Booksellers or Country Mer-
-hin's. Parents, Teachers, Superintendents and  Trustees of Common Schools, Farmers, Mechanics,
and a'l, indeed, who htve any desire to increase their store of useful information on the subjects em-
braced in these vo'umes, are earnestly entreated to examine thin work before  they throw away their
  oney on the trash, or even worse than trash, that is now so rapidly inunda'ing the country.
  From among the numerous recommendatory notices  which the publishers received during the pro
  vss of publication, we have only room to give  the following:
   tin D. Meredith Reese, A. M., M. D., Supe, in-  Tbe volumes of  "The Farmers' Library" and
Frou. _.
  Undent of Common Schools in the City and Coun-
  Ui of New-York.      New-York, Oct. 20, 1846.
Greeley it McElrath :
  Gi;n ilemen : I have examined tbe Popular Lec-
  ires of Dr. Lardneron Science and Art, with much
satisfaction, and take pleasure in  expressing the
opinion that you are doing a valuable service to/he
people of our common country by their publication,
and especially by issuing them at so cheap a t ate.
  To populanzeScienc" and  cheapen Knowledge,
must be regarded by  the philanthropist as worthy
jf the mightiest minds of the age, and to be suc-
cessful in  such efforts, constitutes their authors
public benefactors.  These Lectures of Dr. Lardner
 re addressed to  the common mind, and though
 reading upon the loftiest of the Natural Sciences,
ire so plain and practical, so simple and attractive,
that all who can read may readily profit by their
instructions.  The  clear and familiar illustrations
  d diagrams, which abound in every depaittnent,
we skillfully adapted to the apprehension of youth,
 vho should be encouraged everywhere to reud and
 turfy  them and thus promote their  own happiness
 nd usefulness
  I coild wish that they were found in every School
Library to which their  scientific accuracy and nu-
merous moral reflections upon the wonderful works
of God should be esteemed no smallcoramendation.
But they sitould bt found in every workshop in the
 and;  for Science and Art are  here exhibited in
their true relations; and  the working men of our
country would find here both entertainment and
instruction,  calculated to improve alike their in-
tellects and their morals.        D. M. KEESE.
                State of Michigan.        }
Office of Superintendent of Public Instruction, >
                    Monroe, May 28, 1847   )
  Greeley & McElrath—Gentlemen:  .  .   Your
 (forts, in connection with those of Dr. Lardner, in
preparing so complete an edition of  hie popular
ind attractive Lectures on Science and Art, which
miy he  comprehended by  ordinary  minds, and
  Inch are, nevertheless, replete with instruction,
  e beyond praise.  I shall take great pleasure in
communicating my  official  recommendation of
 hese invaluable Lectures toevery Board of Officers
charged with the purchaseof Township »nd School
Oistrict Libraries through the S ate   I hope they
may reach not only every Town and School District
of this State, but that they may be extensively cir
dilated and read throughout our wide spread coun
'ry.
 'Journal of Agriculture" I shall also take much
pleasure in recommending.  In  their publication
you  have  rendered a grateful  service  to a large
class of your  fellow-citizens, who will read them
with profit and be thankful.
    Very truly yours,        IRA MAYHEW,
          Superintendent of Public Instruction.
                      Rochester, Nov. 2,1846.
  Dear Sir: 1 perused Dr. Lardner's Lectures on
Science and Art, as they appeared in numbers pub-
lished  by  Greeley U McElrath, with much  profit
and satisfaction.
  It has been a source both of complaint and regret
that information upon scientific subjects wa* only
to he obtained through abstruse treatises little adapt
ed to common apprehension.  This, to a great ex-
tent, had closed the popular mind to the attainment
of such information, and prevented the knowledge
of scientific truths from becoming  common and
general.
  I think Dr. Lardner has in these Lectures, to the
extent of the subjects embraced in them, obviated
this evil.  He  has been peculiarly happy in com-
municating information in clear and perspicuous
language, and by  the aid of familiar illustrations
presented  his subjects in a manner both attiactive
and easily comprehended.   In  short  he has been
eminently successful in these Lectures in popular-
izing scientific knowledge.  These volumes contain
a vast amount of  information, presented in an
agreeable manner, and they  are  peculiarly proper
for District School Libraries, and indeed tor every
place  where  they will reach  that popular mind
which they are so well calculated to  enlighten and
improve.  Yours respectfully,
                           F. WHITTLESEY,

  "We know of no publication in this department
of Literature which has succeeded so well in strip-
ping an unwise and erudite philology from a vast
mine of mental wealth, and exhibiting its Httrac-
tious to the delighted gaze  of the ' unlettered hind,1
as well as to the student of Nature's manifold mys
teries.

  "We would be glad to see these interesting dis
sertations in every family, (and we think theii
cheapness renders them easily  accessible to most)
because there is a solidity of matter and a vigor of
style  about them, which will  render them as in-
structive and impressive to succeeding generations
as t > the present."              [The Virginian 
                     IMPORTANT TO LAND-OWNERS

             AND TO FARMERS  AMD  FARMERS'  SONS.

 The  Farmers' Library and Journal of  Agriculture comprises at the present time

Lectures to  Farmers  on  Agricultural  Chemislry.   By  Alexander  Petzholdt.   1
  vol. 8vo.  pp. 108, bound.   Price 50 cents.
 The taste for Scientific Agriculture in the United States has created a demand for the very informa-
lion which these Lecturesof Petzholdt supply  " The motive," says the author, •' which has induced
me to prepare such a ' onrse of Lectures, is the complaint I have heard from many of you, that,being
unacquainted  with the elements of Chemistry, you have found it difficult to understand the questions
which are at the present moment so warmly discussed, respecting the theory and practice of Agricul-
ture. "  This work being less scientific  and technical in its language than Liebig's woik, is on that ac-
count belter adapted for the use of general Farmers, and ought to be first read.  The author in his'Pre-
face says that  a "  rerusal of this work with ordinary  attention will furnish the necessary  amount of
chemical  information fof the purposes  of the Farmer."

The Principles  of  Agriculture.  By  Albert D. Thaer.  Translated from the German
  by Wm. SShaw  and  Cuthbert Johnson.  1 vol. 8vo. pp. 552.   Price, bound. $2 50.
 This justly celebrated work of Baron Von ThaSr is alone worth the full subscription price of the Far-
mers' Library, and yet it is not more than one-third of  what each subscriber to  the Work receives
yearly for his  Bibacription money.  This work of  Von Thaer  was originally written  and published in
the Geinan, tranaUted and published in the French ond  afterward in the English language.  It is pro-
uonced by competent judges to be the most fininhed  Agricultural Book which  has ever been written
and muht to be in the hands of every Farmer in the United States.
 Von Tha£- was educated for a Physician, the practice of which he relinquished  for the more quiet
and philosi pineal pursuits of Agriculture.  Soon after he commenced farming he introduced such  de-
cideo impiovt meats upon his farm that his  fame  was soon known from one  end of Europe to  the
other.

The Book of the Farm:                                          ,.,„,,
Being <t Systematic Work on Practical  Agriculture, on an entirely  New and Original Plan; by HENRV
 St.-.I'H..:-s.  Vtustrated with Portraits of Animals, painted from the life—beautifully engraved; and
 numroiis Wood-Cuts and Plates of Agricultural Implements, so  particularized as to enable Country
 Mechanics to construct  them from the  descriptions.   With copious notes and observations, by iout.
 S Skinner, Editor.  2vols.  8vo.bound.  $5.
 No Farmer who  thirsts for knowledge himself,  or  who  aspires  to have his son rise to the true
"post of honor,"  the dignified station of an intellectual and accomplished Agriculturist, can justifiably
deny hirnhflf such a work as Stephens's Book of the Farm.
 Among the  Engravings which are published in tins Book, we have room to mention the following:
 Views of Farmsteads, or Farm Buildings; Fine Specimens of Cattle, Horses, Oxen, Swine. Cows,
Sheen  Sic ■ Threshing-Machinee,  Sowing-Machines; Gruhberc; The-Farm House;  Servants'House;
Fences- Thorn Hedges;  Field Gates; Stone Dykes;  Embankments;  Draining—an Open Drain in
Grass—Cov-Mcd do ;  Planks and Wedges to prevent sides of Drains falling in, &c. tic. &c. AGRICUL-
TURAL IMPLEMENTS of all kinds;  Various Kinds nf Plows; Sections and  Parts of do.; Shovels;
s?cU affe^Live St-ocTand Cwl H^i.esVrBridle^tt, Collars, te. *c  fcc.fcc
  Every Farm.^ and every gentleman who owns land or cultivate, a garden, is earnestly requested t.
famine thU Work  The whole work, in two splendid octavo volumes, will be completed on the firsi
da, of Jun " 1818   The first volume is now for sale, neatly bound to correspond with Thaer's Princi
pies of Agriculture.

The Journal «f  Agriculture            Promotion of Agricultural Improvement, including the
  Contains the best current V"™*™* d\rnerTca with original contributions from eminent Farrner*
choicest Prtze Essays ™f   Europe.miA«nca w     e         ^   p    ^    $g
and Statesmen.  Edited by John b. skinnbr  t    j „° "  f ,v,,Vn «r» rnlored to life and v«r» mat.
  The Engravings in these volume, are numerous and many of ham are colored to life and very cost
l.*r.™ advaVce and improve the Agriculture of hi. co«-«gR ^jUp* S^xTh" PMutor.. 
THE  NEW-YORK  TRIBUNE.
   We are on the eve of another Presidential Election.—
 Let nor:,j fancy that, since it is approached so calmly.it
 will be conducted sluggishly and terminated without ex-
 citement.  Whoever cherishes  such an illusion mistakes
 tbe character of the American  People  and the impulses
 which sway them.  Equally idle is the imagination that
 Party lines are to be effaced and broken down in this con-
 test—that the prestige of some heroic achievement or the
 glitter of an epaulette is to chase from the popular mind
 all memory of the radical differences of sentiment which
 have  so often arrayed one-half  our countrymen in fierce
 conflict with the other.  Idle  chimeras these! offspring
 of an empty heart or a sickly brain!  With the progress
 of events a  particular measure  may become more or less
 important, the emphatic assertion  of a  certain principle
 more or  less essential, but the  question of questions re-
 mains and will  remain.  At one time, the establishment
 or maintenance of a Sound and Uniform Currency ; at
 another,  the upbuilding and cherishing of new or feeble
 branches of Home Industry; at another, the proper dispo-
 sition of  the Proceeds of the Public Lands; at a fourth,
 Peace or War, Spoliation or Justice; but  underneath all
 these, mightier than any, more enduring than all, lives ev-
 er the elemental difference in  which parties have their
 origin—on one side the  idea that Government should be
 Creative, Constructive, Beneficent ; on the other, the
 negative, skeptical,  do-nothing  element,  whose  axioms
 are 'The best Government is that which  governs least,'
 'The People are inclined to expect too much  from Gov-
 ernment,' 4tc.—which sees in a Canal, a Railroad, a Har-
 bor, a Protective Duly,  only a means of enriching a few
 individuals  at the expense of the community, and which
 cannot conceive how any can be benefited by a  public
 work  without inflicting  injury in at least  equal measure
 upon  others. The  fundamental axioms of this negative
 philosophy are really hostile to Common Roads and Com-
 mon Schools Tequired and sustained by Law, as well as to
 those elements of National well-being against which it
 now directs  the  energies of  a  great party. The antag-
 onism of sentiment growing out  of these conflicting views
 of the nature and true ends of Government cannot, in the
 nature of things, be lastingly compromised; it cannot be
 terminated by  the result of any one election. It must
 be  potentially felt in the party contests and popular agi-
 tations of many years to come.
  On  this and all the great questions growing out of it,
 The Tribune maintains emphatically the doctrines of the
 Whig Party.  It  advocates Protection to Home  Indus-
 try, wherever such Protection may be needed, and to the
 extent of the necessity; a National  Currency, sound
 and of uniform value, composed of Coin  and  Paper in
 such proportions as public interest  and  general conven-
 ience  shall   dictate;  Internal Improvement, by the
 General and  State Governments, each in its own sphere,
 and by Associations, liberally incited thereto by such fa-
cilities as Legislation may safely and justly afford; and
such disposition of the Public Land Proceeds as shall
secure the benefit thereof to the People of all the States
throughout all future time.  Above all, this paper will
' study the things that make for Peace,' and strenuously
oppose the fell  spirit  of War, the Inst of Conquest and
tbe passion for Military Glory, so mortally adverse to all
CLUB
      SEMI-WEEKLY  TRIBUNE.
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 teenth Century.  These views will be faithfully and fear-
 lessly  commended to public favor; while our opposition
 to the Extension of Human Slavery over one foot of soil
 where it has not now a legal existence shall be unsparing,
 uncompromising and subject to no consideration of Party
 advantage or Presidential triumph.  Far sooner will we
 sink with our  principles than succeed  without them,
 however desirable success or however mortifying defeat.
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 pires, the paper  is uniformly stopped, so that no  man
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 will be persecuted by duns or unable to get rid of the paper
 when tired of it.  This rule has given offence to a few pa-
 trons of the non-paying order, but the great majority seem
 to like it better than the old fashion.
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of the time anbscribed and paid for. 
STEPHENS S  BOOK  OF  THE  FARM.
 Extract* from the Critical Notices published in England during  the publication

                                  of the work in London.

                                     From the London Timet.
   " The first part or number of this work has just been published by Messrs. Blackwood.  It is written by
 Mr Henry Stephens, a gentleman already known to the public in his editorial character in the Quarterly
 Journal of Agriculture.  The great merit of the work, as far as it has yet gone, is the intelligible maimer In
 which it is written, and the strong good sense with which it is distinguished.  The proposed arrangement,
 set forth in the plan of the work, is clear and satisfactory; and the whole number is valuable as being the
 result of practical experience and competent theoretic knowledge.  It is a book which will be received with
 gratitude  by those who are really anxious to profit by instruction, and whose anxiety for improvement is
 not impeded by prejudice."  ..." The plan of the work, it may again be observed, is very good—the
 reasoning is logical—the assertions are the results of accurate examination  and repeated  experience.  In
 addition to the information conveyed in the letter-press, the book is ornamented by accurate and handsome
 pistes of agricultural animals, implements of farming, plans of fanning, &.c. &c."
                                   From.the Newcastle Courant.
   " Mr. Stephens's work is divided into three portions.  In the first, the pupil is shown the difficulties he has
 to encounter in acquiring a competent knowledge of farming as a profession, and the most easy and effect-
 ual methods of overcommg these. The  second portion details the various kinds of farming practiced in the
 country, and points out that which the Author reckons the best for adoption under given circumstances.—
 The third and  concluding portion accompanies the young farmer into the world, where it acquaints  him
 how to look about for a proper farm for himself"
                                From Felix Farley's Bristol Journal.
   " When we say that the Author is Mr.  Henry Stephens, we are safe in expressing our conviction that the
 results of his penetration, judgment,  and experience, so placed before the public, will confer an advantage
 on the agricultural interest of no common order.  We therefore predict a large measure of success to the
 Intended work."
                                        From The Argus.
   " We regard it as a national work; and, from the masterly manner in -which  Mr. Stephens handles bis
 subjects, we feel assured it must become a standard one.  His thorough practical knowledge, backed by his
 scientific acquirements, makes the Author's fitness for the task conspicuous; and the unpresuming manner
 in which his talent is displayed enhances its value still more iu our eyes."
                                From the Midland Counties Herald.
   " The entirely practical nature of this work, and the evident care with which it  is produced, will, we
 think, render it one of the most useful publications for the farmer which has yet appeared."
                                        Frorx The Times.
   " The great merit of the work, as far as it has yet gone, is the intelligible  manner in which it is  written,
 and the strong good sense with which it is distinguished.   It is a book which will be received with grati-
 tude by those who are really anxious to profit by instruction, and whose anxiety for improvement ia not
 Impeded by prejudice.
                                 From the Birmingham Advertiser.
   " The farmers of England would do well to possess themselves of this work, for the variety of useful in-
 formation, and the many practical suggestions it contains."
                                      From The Britannia.
   " The two parts now before us are models ot clear, sensible composition, and form  such  an introduction
 to the practice of farming as has never been  published before.   The author  brings to his task a large store
 of knowledge, sound sense and a lucid style."  " We are quite sure that never was any work more called
 for, by the intelligence of the age than this ' Book of the  Farm,' and believe that it  could not have been
 entrusted  to more competent hands, or produced in better style.  We strongly recommend it to all classes
 of agriculturists as a publication of decided utility, and likely to be  most serviceable to them in the suc-
 cessful prosecution of their labors."
                                    From the Sporting Review.
   " The work before  us is one of the most practical results of so  patriotic a spirit.   It is a most wel-
 come addition to our rural literature.   As  it proceeds, we hope to transfer some  of its good things to
 our pages.
                                  From the New Farmers' Journal.
   " On all these important points, no one is  better qualified to fiU the office of a mentor than Mr. Stephens,
 of which  the  well-arranged plan, and  judicious execution, of the book before us, afford irrefragable
 testimony."

                               The Concluding Paragraph.

   Mr. Stephens, tbe Author of tbe above named work, was engaged  for several years in writing
 it.  Ita publicatioo was commenced in London in January, 1842, and  concluded in August, 1844.

 Tbe Author closes the work in the following words:
   " I have now brought to a termination  the task I bad imposed upon  myself in writing this work.
 If you will but follow the prescriptions I have given in it, for conducting the larger operations of
 the field, and for treating the various  animals of the farm ; and—not to mention  the proper plow-
 ing and manuring of the soil—as the practice of every farmer demonstrates the necessity of afford-
 ing dne attention to those most important  because fundamental operations, if you finish off your
 fields in a manner indicating care and neatness—plowing round their margins,  and turning over
 tbe corners ; if you  keep your fences clean and in a state of repair—your fields free of weeds; if
 you give your stock abundance of fresh food at regular intervals in winter, and supply them with
 plenty of clean water on fresh pastures  in summer; if you have the  farm roads always in a ser-
 viceable state,  and everything'about the  steading neat and orderly; if you exhibit skill and taste
 in all these matters, and put  what is called a fine skin on your farm,  you will not fail to earn for
yourself the appellation of a good  and exemplary farmer: and when  you have everything about
you  ' thus well disposed,'  you will find, with Heaiod of old, that profitably, as well aa creditably,
for you ' shall glide away thy rustic year.' " 
 Now publishing in Monthly Parts, in the FARMERS' LIBRARY,
                Price 50 cents each, or $5 per annum,

 THE    BOOK    OF    THE   FARM:
                     BEING A SYSTEMATIC  WORK ON

                PRACTICAL   AGRICULTURE,
             ON AN ENTIRELY NEW AND ORIGINAL PLAN.

                   FY HENRY  STEPHENS,
Editor of " The Quarterly Journal of Agriculture," and " Prize Essays and Transactions of the Highland
                     and Agricultural Society of Scotland."
    ILLUSTRATED WITH PORTRAITS OF ANIMALS,
PAINTED FROM THE LIFE—BEAUTIFULLY ENGRAVED ; AND NUMEROUS WOODCUTS AND
             PLATES OF AGRICULTURAL IMPLEMENTS,
So particularized as to enable Country Mechanics to construct them from the descriptions.
  Of the style, costliness,  and value  of this  celebrated  work, some idea may be
formed, when we state that, in the first  place,  it contains more than  1400 pages,
with upward of Srx Hundred Engravings !  and, further, that in England it  re-
quired more than two years to publish it, and  cost there $24.  This  neat work is
now publishing in the Farmers'' Library. No  farmer who  thirsts for knowledge
himself, or  who aspires to have his son  rise to  the true " post of honor," the digni-
fied station  of an intellectual and accomplished agriculturist, can justifiably deny
himself such a work as is found in the Farmers' Library and Monthly Jour-
nal of Agriculture.
  Among the Six Hundred Engravings  which will be published in this BOOK OF
THE FARM, we have only room to mention the following:—
  Views of Farmsteads, or Farm Buildings;  Fine Specimens of Cattle, Horses,
Oxen, Swine, Cows, Sheep, &c.; Thrashing-Machines ; Sowing-Machines ; Grub-
bers ; The Farm-House ;  Servant's Houses ; Fences; Thorn Hedges;  Field Gates ;
Stone Dykes; Embankments ; Draining—an Open Drain in  Grass:  Covered do.;
Planks and Wedges  to prevent Sides of Drains falling in, &c., &c,  &c.  AGRI-
CULTURAL IMPLEMENTS of all  kinds;  Various Kinds of Plows: Sections
and Parts of do.; Shovels ; Scoops ; Spades ;  Plumb-Level; Swing-Tree? for two
Horses, for  three Horses, for four Horses; Harrows ;  Horse-Hoes; Rollers ; Straw-
Racks ; Water-Troughs ; Straw-Cutters; Shepherd's Crook ; Snow Ptw; Dung-
Hawk ; Scythe and Bend  Sned; Bull's Ring ; Bullock Holder ; Rakes  Form of
Haystacks; Corn-Bruisers; Riddles;  Rope-Spinners; Ladders ; Bean-,  '11;  In-
strument for Topping Turneps; Turnep-Trough for Feeding Sheep ; MovaV  Shed
for Sheep ;  Oil-Cake Breaker; Wheelbarrow ; Turnep Slicer for Sheep ; Ptt  ing
for relieving Cattle  of Choking ;  the Milking-Pail;  Curd-Cutter;  Cheese-Vat;
Churns; Cheese-Press; &c, &c.   Horse-Cart; Liquid-Manure Cart; Single-horse
Tilt-Cart, &c, &c, &c.  Various Operations connected with the Culture of Grain
&c, &c, &c  Also,  Plans for Irrigation; Insects affecting Live Stock and Crops;
Harness, Bridle-Bit, Collars, &c, &c, ire, &c
  [CT* This great Work  is now publishing in  the FARMERS' LIBRARY AND
MONTHLY JOURNAL  OF AGRICULTURE, the subscription price of which
is $5 per annum. Every  farmer, and  every  gentleman who owns  land or culti-
vates a garden, is earnestly requested to examine this Work.
                               GREELEY & McELRATH,  Publishers.
  New York, July 1,1846.