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NATIONAL LIBRARY OF MEDICINE




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ON THE
    OKIGIN  OF  SPECIES:

                OB,

THE CAUSES OF THE  PHENOMENA
       OF


ORGANIC NATUBE.
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               BY

   THOMAS H. HUXLEY, F.R.S., F.L.S.,
PROFESSOR OF NATURAL HISTORY IN THE JEEMTN STREET SCHOOL OF MINES.
           NEW YORK:
D. APPLETOI AND  COMPANY,
          443 & 445 BEOADWAT.
              1863. 
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PEEFACE TO  THE AMEEICAN EDITION.
   The publication of  Mr. Darwin's work on  the
" Origin of Species," whether we consider the import-
ance of the questions it  raises,  the  ability with  which
he treats  them, the  boldness  and  originality  of his
speculations,  or the profound  and  universal interest
which  the book awakened, must be  looked upon as
marking  an era in the progress of science.  But while
it called forth a due  share of candid discussion  and
intelligent criticism, it has been  vehemently and per-
sistently assailed by many who  understood nothing of
its real character; and the subject  has hence been so
overloaded with prejudice and perversion that unscien-
tific people hardly know what to think or believe about
it.  In these  circumstances, those who disencumber the
subject of its  difficulties, simplify its statements, relieve
it of technicalities, and bring it so distinctly within the
horizon of ordinary apprehension that  persons of com-
mon sense may judge for themselves, perform  an in- 
 4        PEEFACE TO THE AMERICAN  EDITION.

 valuable service.  Such  is the character of the present
 volume.
    Prefixed to the English  edition, is  the following
 note from Professor Huxley :  " Mr. J. Aldous Mays,
 who is  taking shorthand notes  of my 'Lectures  to
 Working Men,' has asked me to allow him, on his own
 account, to print those notes for the use of my audience.
 I willingly accede to this request, on  the understanding
 that a notice is prefixed to  the effect that I have no
 leisure  to revise the Lectures,  or to make alterations
 in them, beyond the correction of any important error
 in a matter  of fact."
    The reader will not regret that the Lectures appear
 in this form.  Taken  from the lips of the distinguished
 naturalist, as he addressed an  audience  of ' Working
 Men,' they  have a clearness,  a  directness,  and a  sim-
 plicity which belonged  to the  circumstances of their
 delivery.  In this respect, the  following Lectures are
 incomparable.   Dealing  with the most  abstruse  and
 fundamental questions of mind  and organization, these
 subjects are  nevertheless  presented in so lucid and at-
 tractive a manner as to  impress vividly the commonest
 imagination.
   The gift  of translating the high questions of science
into  popular forms of expression, without sacrificing ac-
curacy and introducing error, is  a very rare one anion o-
scientific men, but Professor  Huxley possesses it in an
eminent degree : his lectures are models of their class. 
                   CONTENTS.

                           —•——
 MO.                                                     PAGE
  I. The Present Condition of Organic Nature    ...   7
 II. The Past Condition of Organic Nature  .     .    .     .29
III. The  Method by which  the Causes of the Present and
      Past Conditions of  Organic Nature are to  be Discov-
      ered.—The Origination of Living Beings   .    .     .52
IV. The  Perpetuation of  Living Beings, Hereditary Trans-
      mission and Variation.......80
 V. The  Conditions of Existence as affecting the Perpetua-
      tion of Living Beings.......102
VI. A Critical Examination of the  Position of Mr. Darwin's
      Work, " On the Origin of Species," in relation to the
      complete Theory of the Causes of the Phenomena of
      Organic Nature........127 
 
LECTURE  I.
 THE  PRESENT  CONDITION OF ORGANIC  NATURE.

   When it was my duty to consider what subject I
would  select for the six lectures which  I  shall now
have the pleasure of delivering to you, it occurred to
me that I could not do better than endeavour to put
before you in a true light, or in what I might perhaps
with more modesty call, that which  I conceive myself
to be the true light, the position of a book which has
been more praised  and  more  abused, perhaps, than
any book which has appeared for some years;—I mean
Mr. Darwin's work on the " Origin of Species."  That
work, I doubt not, many of you have read ;  for I know
the inquiring spirit which is rife among you.  At any
rate, all of you will have heard of it,—some by one kind
of report  and some  by another kind of report;  the
attention of all and the curiosity of all have  been prob-
ably more or less excited on the subject of  that work.
All I can do, and all I  shall  attempt to do, is to put
before you  that kind  of judgment which  has  been
formed by a man, who, of course,  is liable to judge
erroneously ; .but at  any rate,  of one whose business
and profession it is to form judgments upon questions
of this nature. 
8
THE PRESENT CONDITION
  And here,  as it will  always happen when dealing
with an extensive subject, the greater part of my course
—if, indeed, so small a number of lectures can be prop-
erly  called  a  course—must be devoted to preliminary
matters, or rather to a statement of those facts and of
those principles which the work itself dwells upon, and
brings more or less directly before us.  I have no right
to suppose that all or any of you are naturalists ;  and
even if you  were, the misconceptions and  misunder-
standings prevalent even  among naturalists on these
matters would make it desirable that I should take the
course I now  propose to  take,—that I should start from
the  beginning,—that I should endeavour to point out
what is the existing state  of the organic world—that
I should  point  out its past condition—that I should
state what is the precise nature of the undertaking
which Mr. Darwin has  taken in hand;  that I should
endeavour to  show you what are the only methods by
which that undertaking can be brought to an  issue,
and to point out to you how far the  author of the work
in question has satisfied those conditions, how far he has
not satisfied them, how far they are satisfiable by man,
and how far they are not satisfiable  by man.  And for
to-night, in taking up the first part of this question,
I shall endeavour to put before you a  sort of broad
notion of our knowledge of the condition of  the living
world.  There are many ways of doing this.  I might
deal with it  pictorially and  graphically.   Following
the example of Humboldt  in his " Aspects of Nature,"
I might endeavour to point out the infinite  variety of
organic life in every mode of its existence, with  refer-
ence to the variations of climate and the like; and such
an attempt would be fraught with  interest  to us all • 
OF ORGANIC NATURE.
9
but considering the subject before us, such  a course
would not be that best calculated  to assist us.  In  an
argument of this  kind  we must go further and dig
deeper into the matter; we  must endeavour to  look
into the foundations of living Nature, if I may so say,
and discover the  principles involved in some of her
most  secret operations.  I propose, therefore, in the
first place, to take some ordinary animal with which
you are all familiar, and, by easily comprehensible and
obvious examples drawn from it, to show what are the
kind  of  problems which living beings  in general lay
before us; and  I  shall then show you that  the  same
problems are  laid  open to us  by all  kinds  of living
beings.   But,  first, let me say  in what sense  I  have
used  the words " organic nature."  In  speaking of the
causes which lead to our present knowledge of organic
nature, I  have used it almost  as an  equivalent of the
word " living," and for this reason,—that in almost  all
living beings you can distinguish several distinct por-
tions  set apart to do particular things  and work in a
particular way.  These are termed " organs," and the
whole together is called " organic."   And as  it is
universally characteristic of them, this term " organic "
has been very conveniently  ernploj'ed  to  denote the
whole of living nature,—the whole of the plant world,
and the whole of the animal world.
    Few animals can be more familiar to you  than that
whose skeleton is  shown on this diagram.  You  need
not bother  yourselves  with  this  " Eqvus  cabalhis"
written under it; that  is only the Latin  name of it,
and does not make it any better.  It simply means the
common Horse.  Suppose  we wish to  understand  all
about the Horse.   Our first object must be to study
       1* 
10             THE PRESENT CONDITION

the structure  of the animal.  The whole of his body
is inclosed within a hide, a skin covered with hair;  and
if that hide or skin be taken off, we  find a great mass
of flesh,  or  what  is  technically called  muscle,  being
the substance which by its power of contraction enables
the animal  to move.   These muscles move the hard
parts  one upon  the  other,  and  so give  that strength
and power of motion which renders the Horse so useful
to us in the performance of those services in which we
employ him.
   And then, on separating and removing  the whole
of this skin and flesh, you have a great series of bones,
hard structures,  bound  together with ligaments,  and
forming the  skeleton which is represented here.
   In that skeleton there are a number of parts  to be
recognized.  This long series of bones, beginning from
the skull  and ending in the tail, is called the spine,  and
these in front are the ribs; and then there are two pairs
limbs, one before and one behind;  and these are what
we all know as the fore-legs and  the  hind-legs.   If we
pursue our researches into  the interior of this animal,
we  find within the framework of the skeleton a great
cavity, or rather, I should say, two great cavities—one
cavity beginning in the skull and running through the
neck-bones,  along  the  spine, and  ending in the  tail,
containing the brain and the spinal marrow, which are
extremely important organs.  The  second great cavity,
commencing with  the mouth, contains the gullet, the
stomach,  the long  intestine, and all  the  rest of those
internal apparatus which are  essential for digestion ;
and then in  the same great  cavity, there are lodged the
heart and all the great vessels going from it; and, be-
sides that,  the organs  of respiration—the lungs ;  and 
OF ORGANIC NATURE.
11
then the kidneys, and the organs of reproduction, and
so on.   Let us now endeavor to reduce this notion of a
horse that we now have, to  some such kind of simple
expression as can be at once, and without difficulty, re-
tained in the mind, apart from all  minor details.  If I
make a transverse section, that is, if I were to saw a dead
horse across,  I should find that, if I left out the details,
and supposing I took my section through the anterior
region, and through the fore-limbs, I should have here
this kind of section of the body (Fig. 1).  Here would
be the upper part of the
animal—that great mass
of bones that we  spoke
of as the spine  («, Fig.
1).  Here I should have
the alimentary canal  (b,
Fig. 1).  Here I  should
have the heart (c, Fig. 1);
and then  you see, there
would be a kind of double
tube, the whole being in-
closed within the hide;
the spinal marrow would be placed in the upper tube
(a, Fig. 1), and in the lower tube (b, Fig. 1), there would
be the alimentary canal and  the heart; and here  I
shall have the legs proceeding from each side.  For
simplicity's sake,  I represent them,merely as stumps
(e e, Fig. 1).   Now that is a horse—as mathematicians
would  say—reduced to  its most simple expression.
Carry that in your minds, if you please, as a simplified
idea of the structure of the  Horse.   The considerations
which I have now put before  you belong to what we
technically call the ' Anatomy ' of the Horse.  Now,
 
12
THE PRESENT CONDITION
suppose we go to work upon these several parts   iiesh
and hair, and skin and bone, and lay open these vari-
ous organs with our scalpels, and  examine  them  by
means of our magnifying-glasses, and see what we can
make of them.  We shall find that the flesh  is made
up of bundles of strong fibres.  The brain and nerves,
too, we shall find, are made up  of fibres, and these
queer-looking things that  are  called ganglionic cor-
puscles.  If we  take a slice  of the bone and  examine
it, we shall find that it is very like this diagram of a
section of the bone of an  ostrich, though  differing, of
course, in some, details; and if we take any part what-
soever of the tissue, and examine it, we shall find it
all has a minute structure, visible  only under the
microscope.   All  these  parts  constitute  microscopic
anatomy or ' Histology.'  These parts are constantly
being changed ; every part  is constantly growing, de-
caying, and being replaced during the life of the animal.
The tissue is constantly replaced by new material; and
if you go back  to the young state of the tissue in the
case  of muscle, or in the case of skin, or any of the
organs I have  mentioned, you will find that they all
come under the same  condition.   Every one  of these
microscopic  filaments and fibres (I now speak merely
of the general character  of  the whole process)—every
one of these parts—could  be  traced down   to some
modification of a tissue which can  be readily divided
into  little particles of fleshy matter, of that substance
which is composed of the chemical ele-
ments, carbon, hydrogen, oxygen, and ni-
trogen, having such a shape as this (Fig.
2).  These particles, into which all primi-
tive  tissues break up,  are called  cells.
 
OF ORGANIC NATURE.
13
If I were to make a section of a piece of  the  skin  of
my hand, I  should find that it was made up  of these
cells.   If I examine  the fibres which form the various
organs of all living animals, I should  find that all of
them, at one time or other, had been  formed  out of a
substance consisting of similar elements; so that you
see, just as we reduced the whole body in the gross to
that sort of simple expression  given in Fig.  1, so we
may reduce the  whole of the microscopic  structural
elements to a  form of even greater simplicity; just as
the plan of the whole body may be so  represented in a
sense (Fig. 1), so  the primary structure of every tissue
may be represented by a mass of cells (Fig. 2).
    Having thus,  in this sort of general way, sketched
to you  what I may call, perhaps, the architecture  of
the body of the  Horse (what we  term technically  its
Morphology),  I must now  turn  to another aspect.  A
horse is not a mere  dead structure:  it is  an active,
living,  working  machine.   Hitherto  we have, as  it
were, been looking at a steam-engine with the fires out,
and nothing in the boiler;  but the body of the living
animal  is  a  beautifully-formed active machine, and
every part has its different work to do in the  working
of that machine, which is what we call its life.  The
Horse, if you  see him after  his day's  work  is done, is
cropping the grass in the fields, as it may be, or munch-
ing the oats in his stable.   What is  he doing? His
jaws are working as a mill—and a very complex mill
too—grinding the corn, or crushing the grass to a pulp.
As soon as that operation has taken place, the food is
passed down to the stomach,  and there it is mixed with
the chemical fluid called the gastric juice, a substance
which has the peculiar property of making soluble and 
14
THE PRESENT CONDITION
dissolving out the nutritious matter in  the  grass, and
leaving behind those parts which are not nutritious ;
so that you have, first, the mill, then a sort of chemical
digester ;  and then  the  food, thus partially dissolved,
is carried  back by the muscular contractions of the in-
testines into  the  hinder parts  of the body, while the
soluble  portions  are taken up into the  blood.   The
blood is contained in a vast system of pipes, spreading
through the whole body, connected with a force pump,
—the heart,—which, by its position and  by the con-
tractions of its valves, keeps the blood constantly cir-
culating in  one direction, never  allowing it to  rest;
and  then, by means of  this circulation of the blood,
laden as it is with the products of digestion, the skin,
the flesh, the hair, and every other part of  the  body,
draws from it that which it wants, and every one of
these organs  derives those materials which  are neces-
sary to enable it to do its work.
   The action of each of these organs, the performance
of each of these various duties, involve in  their opera-
tion  a continual absorption of the matters necessary for
their support, from the blood, and a constant formation
of waste products, which are returned to the blood, and
conveyed by it to the lungs and the kidneys, which are
organs that have allotted  to them  the office of extract-
ing, separating, and getting rid of these waste products ;
and  thus the general nourishment, labour, and repair
of the whole  machine is kept  up with order and reg-
ularity.   But not only is it a machine which feeds and
appropriates to its own support the nourishment neces-
sary to  its existence—it  is an  engine for locomotive
purposes.  The Horse desires to go  from one place to
another ; and to enable it to do this, it has  those strong 
OF ORGANIC NATURE.
15
contractile bundles of muscles attached to the bones of
its limbs, which are put in motion  by means of a sort
of telegraphic apparatus formed by the  brain and the
great spinal cord running through the spine or back-
bone ;  and to this spinal cord are  attached a number
of fibres  termed nerves, which proceed to all  parts
of the structure.  By means of these the eyes,  nose,
tongue, and skin—all the organs of perception—trans-
mit  impressions or  sensations to the brain, which acts
as a sort  of  great central telegraph-office,  receiving
impressions and sending  messages to all parts of the
body, and  putting in motion the muscles necessary to
accomplish any movement that may  be desired.  So
that here you have an extremely complex and beauti-
fully-proportioned machine, with all its parts working
harmoniously together towards  one common object—
the preservation of the life of the animal.
   Now, note this: the Horse makes up its  waste by
feeding, and  its food  is grass or oats, or  perhaps other
vegetable  products ;  therefore,  in  the long  run, the
source of all  this complex  machinery lies in  the vege-
table kingdom.  But where does the grass, or the oat,
or any other plant, obtain  this nourishing  food-pro-
ducing  material ?  x\t first it is a little seed,  which
soon begins to draw into itself from the earth and the
surrounding air matters which  in  themselves contain
no vital properties whatever ; it absorbs into its own
substance water, an inorganic body ; it draws into its
substance carbonic acid, an inorganic matter ; and am-
monia, another inorganic matter, found in the air ; and
then, by some wonderful  chemical  process, the details
of which chemists do not yet  understand, though they
are near foreshadowing them, it combines them into 
16
THE PRESENT  CONDITION
 one substance, which is known  to us as " Protein," a
 complex  compound of carbon, hydrogen, oxygen, and
 nitrogen, which alone possesses the property of mani-
 festing vitality and of permanently supporting animal
 life.  So  that, you see, the waste products of the  ani-
 mal economy, the effete materials  which  are  contin-
 ually being  thrown  off by all  living beings, in the
 form of organic matters,  are constantly replaced  by
 supplies of  the  necessary repairing  and rebuilding
 materials drawn  from the plants, which  in their turn
 manufacture them, so to speak, by a mysterious com-
 bination of those same inorganic materials.
    Let us trace out the history of the Horse in another
 direction.  After a certain  time, as  the result of sick-
 ness or disease,  the  effect  of accident,  or the conse-
 quence  of old age, sooner or  later, the  animal dies.
 The multitudinous operations  of this  beautiful  me-
 chanism flag in their performance, the Horse loses its
 vigour,  and after passing through the curious series of
 changes comprised in its formation  and  preservation,
 it finally decays,  and  ends  its life by going back into
 that inorganic world  from  which all but an  inappre-
 ciable fraction of its substance was derived.  Its bones
 become mere carbonate  and phosphate  of lime ;  the
 matter of its flesh, and of  its other  parts, becomes, in
 the long run, converted into carbonic acid, into water,
 and into ammonia.  You  will now, perhaps, under-
 stand the curious relation of the animal with the plant,
 of  the  organic  with  the  inorganic world, which  is
 shown in this diagram.
    The plant gathers these inorganic  materials together
and makes them up into its own  substance.  The ani-
mal eats the plant and  appropriates the nutritious por- 
OF ORGANIC NATURE
17
INORGANIC WORLD.
Carbonic Acid.        "Writer.   Ammonia.     Salines.
VEGETABLE WORLD.      (Fig. S.)     ANIMAL WORLD.
tions  to  its own sustenance, rejects  and gets rid of
the useless matters ; and, finally, the animal itself dies,
and its whole body is decomposed and  returned  into
the inorganic world.   There is thus a constant circula-
tion from  one  to the other, a continual  formation of
organic life from inorganic matters, and  as constant a
return of living bodies to the inorganic world ; so that
the materials of which our  bodies are  composed  are
largely, in all  probability, the substances which  con-
stituted the matter  of long extinct creations, but which
have  in the interval constituted a part of the inorganic
world.
    Thus we come  to the conclusion, strange at  first
sight, that the Matter constituting the living world is
identical with that which forms  the  inorganic world.
And  not less true is it, that, remarkable as are  the
powers or, in other words, as are  the Forces which are
exerted by living beings, yet all these forces are either
identical with those which exist in the inorganic world,
or they are convertible into them ; I mean in just  the
same  sense as the  researches of physical philosophers
have  shown that heat is convertible  into  electricity, 
18
THE PRESENT CONDITION
 that electricity is convertible into magnetism, magne-
 tism into mechanical  force or chemical force, and any
 one of them with the other, each being measurable in
 terms of the  other,—even so, I  say, that great law is
 applicable  to the living world.   Consider why is the
 skeleton of this horse capable of  supporting the masses
 of flesh and the various organs forming the living body,
 unless it is  because of the action of the  same forces of
 cohesion which  combines together the particles of mat-
 ter composing this piece of chalk ?   What is  there in
 the  muscular contractile power of the animal but the
 force which is  expressible, and which is in a certain
 sense convertible, into  the force of gravity which it
 overcomes ?   Or, if you go to more  hidden processes,
 in what does the process of digestion differ from those
 processes which are carried on in the  laboratory of the
 chemist?   Even if  we  take  the most  recondite and
 most complex operations of animal life—those of the
 nervous system, these of late years have been shown to
 be—I do not say identical in  any sense with the elec-
 trical processes—but this  has been shown, that they
 are in some  way or other associated with them ;  that is
 to say, that  every amount of nervous action is accom-
 panied by a certain amount of electrical disturbance in
 the particles of the nerves in which that nervous action
 is  carried on.  In this way the  nervous action is re-
 lated to  electricity in  the same  way that heat is re-
 lated to electricity;  and the  same  sort of argument
 which demonstrates the  two latter to  be related to one
 another shows that the nervous forces are correlated to
electricity ;  for  the  experiments  of M.  Dubois Rey-
mond and others have shown that whenever  a nerve
is in a state of  exciment,  sending  a message  to  the 
OF ORGANIC NATURE.
19
muscles or conveying an impression  to the brain, there
is a disturbance of the electrical condition of that nerve
which does not exist at other times; and there are  a
number of other facts and phenomena of that sort;  so
that we come to the broad conclusion that not only as
to living matter itself, but as to the forces that matter
exerts, there is a close relationship between the organic
and  the  inorganic world—the difference between them
arising from the diverse combination and disposition
of identical  forces, and not  from any primary diver-
sity, so far as we can see.
   I said just  now that the Horse eventually died and
became converted into  the  same inorganic substances
from  whence all but an inappreciable fraction  of its
substance demonstrably originated,  so that the actual
wanderings of matter are as remarkable as  the trans-
migrations of the soul fabled by Indian tradition.  But
before death has occurred, in the one sex or the other,
and  in fact in both, certain products or parts of the
organism have been set free,  certain  parts of the organ-
ism of the two sexes have come into contact with one
another,  and from that conjunction, from that union
which then takes place, there results the  formation of a
new being.   At stated  times the mare, from a particu-
lar part of the interior of her body, called the ovary,
gets rid of a minute particle of matter comparable  in
all essential respects with that which we called a cell a
little while since, which  cell contains a kind of nucleus
in its centre, surrounded by a clear space and by a vis-
cid mass of protein  substance (Fig. 2);  and  though it
is different in appearance from the eggs which we are
mostly acquainted with, it is really an  egg.  After  a
time this minute particle of matter, which may only be 
20
THE PRESENT CONDITION
a small fraction of a grain in weight, undergoes a series
of changes,—wonderful, complex changes.  Finally,
upon its surface  there is fashioned a little elevation,
which afterwards becomes  divided and marked by a
groove.  The lateral boundaries of the groove  extend
upwards and downwards, and at length give rise to a
double  tube.  In the upper smaller  tube the spinal
marrow and brain are fashioned ;  in the lower, the ali-
mentary canal and heart, and at length two pairs  of
buds  shoot out at the sides of the body, which are the
rudiments of the limbs.  In fact a true drawing of a
section of the  embryo in this state would in all essen-
tial respects resemble that diagram of a horse reduced
to its simplest expression, which I first placed before
you (Fig. 1).
   Slowly  and gradually  these  changes  take place.
The whole of the  body,  at first, can be broken up into
" cells," which become  in  one place  metamorphosed
into  muscle,—in another place into gristle and bone,
—in another place into  fibrous tissue,—and in another
into hair; every  part  becoming  gradually and  slowly
fashioned, as if there were  an artificer at work at each
of these  complex structures that we have mentioned.
This embryo, as it is called, then passes into other con-
ditions.  This diagram represents the embryo of a dog ;
and  I should tell you that there is a time when the
embryos of  neither  dog, nor horse, nor porpoise, nor
monkey, nor man, can be distinguished by any essen-
tial feature one from the other;  there is a time when
they each and all  of them resemble this one of the Doo\
But  as development advances, all the  parts acquire
their  speciality, till at length you have the embryo
converted into the form  of the parent from which it 
OF ORGANIC NATURE.
21
started.  So that you see, this living animal, this horse,
begins its existence as a minute particle of introgenous
matter, which, being supplied with nutriment (derived,
as I have shown,  from the inorganic world), grows up
according to the special  type and construction of its
parents,  works and  undergoes a constant waste,  and
that waste is made  good by  nutriment  derived from
the inorganic world; the waste given off in this way
being  directly added  to the  inorganic  world;   and
eventually the  animal itself dies, and, by the  process
of decomposition,  its whole  body is returned to those
conditions of inorganic matter in which its substance
originated.
   This, then,  is  that which is  true  of every living
form,  from the lowest plant to the highest animal—to
man himself.  You might define  the life of every one
in exactly the same  terms as  those which I have now
used;  the  difference  between the  highest and  the
lowest being simply  in the complexity of the develop-
mental changes, the variety of the structural forms,
the diversity of the  physiological functions which are
exerted by each.
    If I were to take an oak tree as a  specimen of the
plant world, I should find that it originated in an acorn,
which, too, commenced in a cell; the  acorn  is placed
in the ground, and  it very speedily begins to absorb
the inorganic matters I have named, adds enormously
to its bulk, and we can see it, year after year,  extend-
ing itself upward and downward, attracting and ap-
propriating to itself inorganic  materials,  which  it vivi-
fies, and eventually, as  it  ripens,  gives off its  own
proper acorns, which again run the same course.   But
I need not multiply examples—from the highest to the 
22             THE PRESENT CONDITION

lowest the essential features of life  are the same, as I
have described in each of these cases.
   So much, then, for  these particular features of the
organic world, which you can  understand and compre-
hend, so  long as  you  confine  yourself to one sort of
living being, and study that only.
   But, as  you know, horses  are not the  only living
creatures in the  world; and  again,  horses,  like  all
other animals, have certain limits—are confined to a
certain area on the surface of the  earth on which we
live—and, as that is  the simpler matter, I  may take
that  first.  Li its wild state, and before the discovery
of America, when the natural state of  things was inter-
fered with by the Spaniards, the Horse was  only to be
found in parts of the  earth which  are known to geo-
graphers as the Old World  ; that is to say, you might
meet with horses in Europe, Asia, or Africa;  but there
were none in Australia, and  there  were none whatso-
ever in the whole continent of  America, from Labrador
down to Cape  Horn.  This is an  empirical fact,  and
it is  what is called, stated  in  the way I have given it
you, the " Geographical Distribution " of the Horse.
   Why horses should be found in Europe, Asia, and
Africa, and not in America, is  not obvious; the expla-
nation that the conditions of life  in America are un-
favorable to their existence, and that, therefore, they
had  not been created there, evidently does not apply ; for
when the invading Spaniards, or our own yeomen farm-
ers,  conveyed horses  to these countries for  their own
use,  they were found to thrive well  and multiply very
rapidly; and many are even now running wild in those
countries, and in a perfectly natural condition.  Now,
suppose we were to do for  every animal what we have 
OF ORGANIC SPECIES.
23
here done for the Horse—that is, to mark off and dis-
tinguish the particular district or region to which each
belonged;  and supposing we tabulated all these results,
that would be called the Geographical Distribution of
animals, while a corresponding study of plants would
yield as a result the Geographical Distribution of plants.
    I pass  on from  that now, as  I merely wished to
explain to you what I meant by the use of the term
" Geographical Distribution."  As I said, there is another
aspect, and a much more  important one, and  that is,
the relations  of  the various animals to one  another.
The Horse is a very well defined matter-of-fact sort of
animal, and -we are all pretty familiar with its structure.
I  dare  say it may have struck you, that it resembles
very much  no other member of the animal kingdom,
except perhaps the Zebra or the Ass.  But  let me ask
you to look along these diagrams.  Here is the skeleton
of the Horse, and here the skeleton of the Dog.   You
will notice  that we have in the Horse a skull,  a back-
bone and ribs, shoulder-blades and haunch-bones.  In
the fore-limb, one upper arm-bone, two fore arm-bones,
wrist-bones (wrongly  called knee),  and  middle hand-
bones, ending in the three  bones  of a finger,  the last
of which is sheathed in the horny hoof of the fore-foot:
in the hind-limb, one thigh-bone, two leg-bones, ankle-
bones, and middle foot-bones, ending in the three bones
of a toe, the last of which is encased in the hoof of the
hind-foot.   Now turn  to the Dog's skeleton.  We find
identically the same  bones, but  more of them, there
being more toes in each foot, and hence more toe-bones.
    Well, that  is  a very, curious  thing!  The  fact  is
that the Dog and the  Horse—when one  gets a look  at
them without the outward impediments of  the skin— 
24
THE PRESENT CONDITION
are found to be made in very much the same  sort of
fashion.  And  if I were to make a transverse  section
of the Dog, I should find the same  organs that I have
already shown you as  forming parts  of the  Horse.
Well, here is another skeleton—that of a kind of Lemur
—you see he has just the same bones ; and if I were
to make a transverse section of it, it would be just the
same again.   In your mind's eye turn him  around, so
as to put his backbone in a position inclined  obliquely
upwards  and forwards,  just as in the next  three dia-
grams, which represent  the skeletons of an Orang, a
Chimpanzee, a Gorilla,   and you find you have  no
trouble in identifying the bones throughout; and lastly
turn to the end of the series, the diagram  representing
a man's skeleton, and still you find no great structural
feature essentially altered.  There are the same bones
in the same  relations.   From  the  Horse we pass  on
and on, with  gradual steps,  until we  arrive  at last at
the highest  known  forms.   On the other hand, take
the other line of diagrams, and pass from  the Horse
downwards in the scale  to this fish ;  and  still,  though
the modifications are vastly greater, the essential frame-
work of the organization remains unchanged.  Here,
for instance,  is a Porpoise ; here is its strong backbone,
with the cavity running  through  it, which contains the
spinal cord;  here are the ribs, here the shoulder-blade;
here is the little  short  upper-arm bone, here are the
two forearm  bones, the wrist-bone, and the finger-bones.
   Strange, is it not, that the Porpoise should have in
this  queer looking affair—its  flapper  (as it  is called),
the same fundamental elements  as  the fore-leg of the
Horse or the Dog, or the Ape  or Man ; and  here you
will notice a very curious thing—the hinder limbs are 
OF ORGANIC NATURE.
25
 absent.  Now, let us make  another jump.  Let us go
 to the  Codfish: here you see is  the  forearm, in  this
 large pectoral fin—carrying your mind's eye onward
 from the flapper of the Porpoise.  And here you have
 the hinder limbs restored in the shape  of these ventral
 fins.  If I were to make a transverse section of this, I
 should find just the same organs that  we have before
 noticed.  So that, you see, there comes out this strange
 conclusion as the result of our investigations, that the
 Horse, when examined  and compared with  other  ani-
 mals, is found by no means to stand alone in nature;
 but that there are an enormous number of other crea-
 tures which have backbones, ribs, and legs, and other
 parts arranged in the  same general manner, and in all
 their formation exhibiting the same broad peculiarities.
   I  am sure that you cannot have followed me even
 in this  extremely  elementary exposition of  the  struc-
 tural relations of animals, without seeing what I have
 been driving at all through, which is to show you that,
 step by step, naturalists  have  come to the idea of a
 unity of plan, or conformity of construction, among
 animals which appeared at first sight to be extremely
 dissimilar.
   And here you have evidence of such a unity of plan
 among  all the animals  which  have  backbones,  and
 which  we technically call Vertehrata.  But  there  are
 multitudes of other animals, such as  crabs, lobsters,
 spiders, and so on, which we term Annulosa.  In these
 I could not point out to you the parts that correspond
 with those of the Horse—the backbone, for instance—
 as they are constructed upon a very different principle,
which  is also common to all of them ; that  is to say,
the  Lobster, the Spider, and  the Centipede, have  a
        2 
26
THE PRESENT CONDITION
 common  plan running through  their whole arrange-
 ment, in  just the same way that the Horse, the Dog,
 and the Porpoise assimilate to each other.
    Yet other  creatures—whelks, cuttlefishes,  oysters,
 snails,  and all their tribe {Mollusca)—resemble one
 another in the same way, but  differ from both Verte-
 brata  and Annulosa; and the like is true of  the ani-
 mals called Cvelcnterata (Polypes) and  Protozoa (ani-
 malcules and sponges).
    Now by pursuing this sort of comparison, naturalists
 have arrived  at  the conviction that there are—some
 think  five, and some  seven—but certainly  not  more
 than the  latter number—and perhaps it is simpler to
 assume five—distinct  plans or constructions  in  the
 whole of the animal world ; and that the hundreds of
 thousands of species of creatures on the surface of the
 earth,  are all reducible to  those five, or, at most, seven,
 plans of organization.
    But can we go no  further than that ?  When one
 has got so far, one is tempted to go on  a step  and in-
 quire whether we cannot go back yet further and bring
 down  the whole to modifications  of one primordial
 unit.   The anatomist cannot do this ; but if he call to
 his aid the study of development, he can  do it.  For
 we shall find that, distinct as those plans are, whether
 it  be a porpoise  or man, or lobster,  or  any of those
 other kinds I have mentioned, every one begins its ex-
 istence with one and the same primitive form,—that of
 the egg, consisting,  as we  have seen, of  a introgenous
 substance, having a small  particle  or nucleus  in  the
 centre of it.  Furthermore, the earlier changes of  each
 are substantially the same.  And it is in this that lies
that true " unity of organization " of the animal king- 
OF ORGANIC NATURE.
27
dom which  has been guessed at and fancied for many
years; but which it has been left  to the present time
to be demonstrated by the  careful study of develop-
ment.   But is it  possible to go another step further
still, and  to show that in  the same way the whole of
the organic world is  reducible  to  one primitive con-
dition of form ?  Is there  among the plants the  same
primitive form of organization,  and is  that  identical
with that of the animal kingdom ?  The reply to that
question, too,  is not uncertain or doubtful.   It is now
proved  that every plant begins its existence under the
same form ; that is to say, in that of a cell—a particle
of introgenous matter having  substantially the  same
conditions.  So that if you  trace back the oak to its
first germ, or a man,  or a horse, or lobster, or oyster,
or any other animal you choose to name, you shall find
each and all  of these commencing their existence in
forms essentially similar  to  each other: and, further-
more, that the first processes of growth, and many of
the subsequent modifications, are essentially the  same
in principle in almost all.
    In conclusion, let me, in  a few words, recapitulate
the positions which I have laid down.   And you must
understand  that I  have not been talking mere theory ;
I have  been  speaking of matters which are as plainly
demonstrable  as the commonest  propositions of Euclid
—of facts that must form the basis  of all speculations
and beliefs in  Biological science.   We have gradually
traced down all organic forms, or, in other wTords, we
have  analyzed the present condition of  animated na-
ture, until we  found that each species took its origin in
a form similar to that  under which all the others com-
mence their existence.  We  have found the whole of 
28      PRESENT CONDITION OF ORGANIC NATURE.

the vast array of living forms, with which we are sur-
rounded, constantly growing, increasing, decaying, and
disappearing ; the animal constantly attracting, modify-
ing, and applying to its sustenance the matter of the
vegetable kingdom, which derived its support from the
absorption and conversion of inorganic matter.  And
so constant and universal is this absorption, waste, and
reproduction, that it may be said with perfect certainty
that there is left in no one of our bodies at the present
moment a millionth  part of the matter of which they
were  originally formed!  We have seen, again, that
not only is  the living matter  derived  from the inor-
ganic world, but that the forces of that matter  are all
of them correlative with  and convertible into those of
inorganic nature.
   This, for our present  purposes, is the best view of
the present condition of organic nature which I can lay
before you : it  gives  you the great outlines of  a vast
picture, which you must fill  up by your own  study.
   In  the next lecture  I shall endeavour in the same
way to go back into the past, and to sketch in the same
broad  manner the history of life in epochs preceding
our own. 
LECTURE  II.
     THE PAST CONDITION OF ORGANIC NATURE.

    In the lecture which I delivered last Monday even-
ing, I endeavoured to sketch in a very brief manner,
but as well as the time  at my disposal would permit,
the present condition of organic  nature, meaning by
that large title simply an indication of the great, broad,
and general principles which are to be discovered by
those who look attentively  at the phenomena of or-
ganic nature as at present displayed.   The general re-
sult of our  investigations might be summed up thus:
we found that  the multiplicity of the forms of animal
life, great as that may be, may be reduced to a com-
paratively few primitive plans or types of construction;
that a further study of the  development of those dif-
ferent forms revealed to us  that they were  again re-
ducible, until we at last  brought the infinite diversity
of animal, and  even vegetable life, down to the primor-
dial form of a single cell.
    We  found that our analysis of the organic world,
whether  animals or plants,  showed, in the long run,
that they might both be reduced into, and  were, in
fact, composed  of the same constituents.   And we saw
that the plant obtained the  materials  constituting its 
30
THE PAST CONDITION
 substance by a peculiar combination of matters belong-
 ing  entirely  to the  inorganic  world ; that, then,  the
 animal  was constantly  appropriating the  nitrogenous
 matters of the plant  to its  own  nourishment, and re
 turning them back to the inorganic world, in what we
 spoke of  as  its waste;  and  that,  finally, when  the
 animal  ceased  to exist, the  constituents of its  body
 were dissolved and transmitted to that inorganic world
 whence they had  been at first abstracted.  Thus  we
 saw  in  both  the blade of grass and the horse but  the
 same elements differently combined  and arranged.  We
 discovered a continual circulation going on,—the  plant
 drawing in the elements of inorganic nature and com-
 bining them into food for the animal creation ; the ani-
 mal  borrowing from  the plant the matter for its own
 support, giving off during its life products which  re-
 turned immediately to the inorganic world ; and  that,
 eventually, the constituent materials of the whole struc-
 ture  of both  animals and plants were thus returned to
 their original source: there  was a constant passage
 from one state of existence  to another, and a returning
 back again.
   Lastly,  when we  endeavoured to form some notion
 of the nature of the forces  exercised by living beings,
 we discovered that they—if not capable of being sub-
 jected  to the same minute analysis as the constituents
 of those beings themselves—that they were correlative
 with—that they were the equivalents of the forces  of
 inorganic  nature—that  there  were, in the sense  in
which the  term is now used, convertible with them.
That was our general result.
  And  now,  leaving  the Present, I must  endeavour
in the same manner to  put before  you  the facts that 
                 OF ORGANIC NATURE.               31

are to be discovered in the Past  history of the  living
world, in the  past  conditions of organic nature.  We
have, to-night, to deal with the facts of that history—
a history involving periods of time  before which our
mere human records sink into  utter insignificance—a
history the variety and physical  magnitude of  whose
events cannot even be foreshadowed  by the history of
human life  and human  phenomena—a history  of the
most varied aud complex  character.
    We must  deal  with the  history,  then,  in the first
place, as we should deal with all  other histories.  The
historical student knows  that his first business should
be  to inquire  into the validity of  his evidence, and the
nature of the  record  in which the evidence is contain-
ed, that  he  may be able  to form  a proper  estimate of
the  correctness  of the conclusions  which  have been
drawn from that evidence.  So, here, we must pass, in
the first  place, to the consideration of a matter  which
may  seem foreign to the question  under discussion.
We must dwell upon the nature of  the records, and
the credibility of the evidence they contain ; we must
look to  the completeness or incompleteness of those
records  themselves, before we turn to that  which they
contain and reveal.   The  question of the credibility of
the history,  happily for us, will  not  require much con-
sideration, for, in this history, unlike those of human
origin, there can be  no cavilling, no  differences as to
the reality and  truth of the facts of which it is made
up ; the  facts state themselves, and are laid out clearly
before us.
    But,  although one of the greatest difficulties  of the
historical student is cleared out of our path, there are
other difficulties—difficulties in rightly interpreting the 
32
THE PAST CONDITION
 facts as they are presented to us—which may be com-
 pared with the greatest difficulties of any other kinds
 of historical study.
    What is this record of the past history of the globe,
 and wdiat are the questions which are involved in an
 inquiry into its completeness or incompleteness \  That
 record is composed of mud ;  and the question which
 we have to investigate this  evening resolves itself  into
 a question of the formation of mud.  You may think,
 perhaps, that  this is a  vast step—of almost from the
 sublime  to the ridiculous—from  the  contemplation of
 the history of the past ages of the wTorld's existence to
 the  consideration of the  history of the formation of
 mud !   But, in nature, there is nothing mean and un-
 worthy of attention  ; there is nothing ridiculous or con-
 temptible in any of her works ; and  this inquiry,  you
 will soon see, I hope, takes us to the very root  and
 foundations of our subject.
    How,  then, is mud  formed ?  Always, with some
 trifling  exception, which I need  not consider now—
 always, as the result of the action of water, wearing
 down and disintegrating the surface of the earth  and
 rocks with which it comes  in contact—pounding  and
 grinding it down, and carrying the particles  away to
 places  where they cease to  be disturbed  by this me-
 chanical  action, and where they can subside and rest.
For the ocean, urged by winds, washes,  as we know,
 a long extent of coast, and every wave, loaded as it is
 with particles of sand and gravel as it breaks upon the
shore, does something towards the disintegrating pro-
cess.  And thus, slowly but surely, the hardest rocks
are gradually  ground down to a powdery substance;
and the mud thus formed, coarser or finer, as the case 
OF ORGANIC NATURE.
33
may be, is carried by the rush of the tides, or currents,
till it  reaches the comparatively  deeper parts of the
ocean, in which  it can  sink to the bottom, that  is, to
parts where there is a depth of about fourteen or fifteen
fathoms, a depth at which the water is, usually, nearly
motionless, and  in -which, of course, the finer particles
of this detritus, or  mud,  as  we  call it, sinks to the
bottom.
   Or, again, if you take  a river, rushing down  from
its  mountain  sources, brawling  over the stones and
rocks that intersect  its  path, loosening, removing, and
carrying with it in  its downward course the pebbles
and  lighter matters from its banks, it crushes and
pounds down the  rocks  and earths in precisely the
same way as the wearing action of the sea waves.   The
matters forming  the deposit are torn from the mountain-
side and whirled  impetuously into the  valley,  more
slowly over  the plain, thence into the estuary, and from
the  estuary they are swept into the sea.   The coarser
and heavier fragments are obviously deposited  first,
that is, as soon  as the current begins to lose  its  force
by becoming amalgamated with  the  stiller depths of
the ocean, but the finer and lighter particles are carried
further on,  and  eventually deposited in a deeper and
stiller portion of the ocean.
   It clearly follows from this  that  mud gives  us a
chronology; for it is evident that supposing this, which
I now sketch, to be the sea bottom, and supposing this
to be a coast-line; from the washing action of the sea
upon the rock,  wearing and grinding it down into a
sediment of mud, the  mud will be carried down, and
at length, deposited  in the deeper parts of this sea bot-
tom, where  it will form a layer ; and  then, while that
         2* 
34
THE PAST CONDITION
first layer is  hardening, other mud which is  coming
from the same source will, of course, be carried to the
same place ; and, as it is quite impossible for it to get
beneath the layer already there, it deposits itself above
it, and forms another layer, and in that way you grad-
ually have la}Ters of mud constantly forming and hard-
ening one above the other, and conveying  a record of
time.
    It is a necessary result of the  operation of  the law
of gravitation that the uppermost layer  shall be the
youngest and the lowest the oldest, and  that the differ-
ent beds shall be older at any particular point or  spot
in exactly the ratio of their  depth from the  surface.
So that if they were upheaved afterwards, and you had
a series of these different layers of mud, converted  into
sandstone, or limestone, as the case might be, you might
be sure that the bottom layer was deposited first,  and
that the upper layers were formed afterwards.   Here,
you see, is the first step in the history—these layers of
mud give us an idea of time.
  The  whole surface of the  earth—I  speak broadly,
and leave out minor qualifications—is made up  of such
layers of mud, so hard, the majority of them, that we
call them rock, whether limestone or sandstone, or
other varieties of rock.   And,  seeing that every part
of the crust of the earth is made up in this way,  you
might think that the determination of the chronology,
the fixing of the time which it  has taken  to  form  this
crust is a comparatively simple matter.  To  take a broad
average, ascertain how fast the mud is deposited upon
the bottom of the sea, or in the  estuary of  rivers ; take
it to be an inch, or two, or three indie's a year, or'what-
ever you may roughly estimate it at; then take  the 
OF OKGANIC NATURE.
35
total thickness of the whole series of stratified rocks,
which  geologists estimate at twelve or thirteen miles,
or about seventy thousand  feet, make a sum in short
division, divide the total thickness by that of the quan-
tity deposited in one year, and the result will, of course,
give you the number of years which the crust has taken
to form.
   Truly, that looks  a very simple process!   It would
be so  except for  certain difficulties, the very first of
which is that of finding  how rapidly sediments are de-
posited ; but the main difficulty—a  difficulty which
renders any certain calculations of such a matter out
of the question—is this, the sea-bottom on which the
deposit takes place is continually shifting.
   Instead of the surface of the earth being that stable,
fixed thing  that it is popularly believed to  be, being,
in common parlance, the very emblem of fixity itself,
it is  incessantly moving, and is, in fact, as unstable as
the surface of the sea, except that its undulations are
infinitely slower and  enormously higher and deeper.
   Now, -what is the effect of  this oscillation ?  Take
the case to which I have previously referred.  The finer
or coarser sediments that  are  carried  down by  the
current of the river, will only be carried out a certain
distance, and eventually, as we have  already seen, on
reaching the stiller part of the ocean, will be deposited
at the bottom.
   Let C y (Fig. 4) be the sea-bottom, y D the  shore,
x y the sea-level, then the coarser  deposit will subside
over the region B, the finer over  A, while beyond A
there will be no  deposit at all; and, consequently, no
record will be kept, simply because no deposit is going
on.  Now,  suppose that the whole land, C, D, which 
30
THE PAST CONDITION
we have regarded as stationary, goes down, as it does
so, both A and B go further out from the shore, which
                                         Fig. 4.
will be at y\ xl y\ being the new sea-level.  The con-
sequence will be that the layer of mud (A), being now,
for the most part, further than the force of the current
is strong enough to convey even the finest  debris, will,
of course, receive no more deposits, and having attained
a certain thickness will now grow no thicker.
    We should be misled in taking the thickness of that
layer, whenever  it may be exposed to our view, as a
record of time in the manner in which  we are now
regarding this subject,  as  it  would give  us only  an
imperfect and partial record  it would seem to  repre-
sent too short a period of time.
    Suppose, on the other  hand, that the land (C  D)
had gone on rising slowly and gradually—say an inch
or two inches in the course  of  a century,—what would
be the practical effect of that  movement ?  Why that
the sediment A and B which has been already depos-
ited, would eventually be brought nearer to the  shore-
level, and again subjected  to the wear and tear of the
sea; and directly the sea begins to act upon it, it would
of course soon  cut up and  carry it away, to a greater
or less extent, to be re-deposited further out. 
OF ORGANIC NATURE.
37
   Well, as there  is, in all probability, not one single
spot on the whole  surface of the earth, which has not
been up and down in this way a great many times, it
follows  that the thickness of the deposits  formed  at
any particular spot cannot  be taken (even supposing
we had  at first obtained correct data as to the rate at
which they took place), as affording reliable  informa-
tion as  to the period of time occupied in its deposit.
So that  you see it is  absolutely necessary from  these
facts, seeing that our record entirely consists of accumu-
lations of mud, superimposed one on  the other ;  seeing
in the next place that any particular  spots on which
accumulations  have  occurred,  have been  constantly
moving up and down, and sometimes out of the reach
of a deposit, and at other times its own deposit broken
up and  carried away, it follows that our record  must
be in the highest degree imperfect, and we have hardly
a trace left of thick deposits, or any definite knowledge
of the area that they occupied in a great many  cases.
And mark this!   That supposing even that the whole
surface  of  the earth had been accessible  to the geolo-
gist,—that man had had access to  every part  of the
earth, and had made sections  of the whole,  and put
them all together,—even then his record must of neces-
sity be  imperfect.
   " But to how much has man really access ?  If you
will look at this  Map  you will see that it represents
the proportion of the sea to  the earth:  this  coloured
part indicates all  the dry land, and  this other portion
is the water.   You will notice at once that the water
covers  three-fifths of the whole surface of the  globe,
and has covered it in the same manner ever since man
has  kept any- record of his own  observations, to  say 
38
THE PAST CONDITION
nothing of the minute period during which he has cul-
tivated geological inquiry.  So  that three-fifths of the
surface of the earth is shut out from us because it is
under the sea.  Let us look at the other two-fifths, and
see what are the countries  in which anything that may
be termed searching geological inquiry has been carried
out:  a good deal of  France, Germany, and Great Brit-
ain and Ireland, bits of Spain, of Italy, and of Russia,
have  been examined, but of the whole great mass  of
Africa, except parts of the southern extremity, we know
next to nothing;  little bits of India, but of the greater
part  of the Asiatic  continent  nothing; bits  of the
Northern  American States and of Canada, but of the
greater part of the  continent of  North America, and
in still larger proportion, of South America, nothing!
   Under these circumstances, it follows that  even with
reference to that  kind of imperfect information which
wTe can possess, it is only about the ten thousandth part
of the accessible parts of the earth that has been exam-
ined  properly. Therefore, it  is with justice  that  the
most  thoughtful  of those who  are concerned in these
inquiries insist continually upon the  imperfection  of
the geological record; for, I repeat,  it is  absolutely
necessary, from the nature of things, that that record
should be  of the most fragmentary and imperfect char-
acter.  Unfortunately this  circumstance has been con-
stantly forgotten.   Men of science,  like young colts
in a fresh  pasture, are  apt  to be exhilarated on  being
turned into  a  new field of  inquiry, and to go  off at a
hand-gallop, in total disregard of hedges and ditches,
losing sight of the real limitation of their  inquiries,
and to forget the extreme imperfection of what  is really
known. Geologists have imagined that they could tell 
OF ORGANIC NATURE.
39
us what was going on at all parts of the earth's surface
during a given epoch ; they have talked of this deposit
being contemporaneous with that  deposit, until, from
our little local histories of the changes at limited spots
of the earth's surface, they have constructed a universal
history of the globe as full of wonders and portents as
any other story of antiquity.
   But what does this attempt to construct a universal
history of the globe  imply ?  It implies that we shall
not only have a precise knowledge of the events which
have occurred at any particular point, but that we shall
be able to say what events, at any  one spot, took place
at the same time with those at other spots.
   Let us see  how far that is in the nature of things
practicable.  Suppose  that  here I make a  section of
the Lake of Killarney, and here the section of another
lake—that of Loch Lomond in  Scotland for instance.
The rivers that flow into them are constantly  carrying
down deposits of mud, and beds, or strata, are  being as
constantly formed, one above the other, at the bottom
of those lakes.  Now, there is not a shadow of doubt
that in these two lakes the upper beds are all older than
the lower—there is no doubt about that; but what does
this  tell us about the age  of any given bed  in Loch
Lomond, as compared with that of any given bed in
the Lake of Killarney ?  It is, indeed, obvious that if
any two sets of deposits are separated  and discontinu-
ous, there is absolutely no means whatever given  you
by the nature of  the deposit of  saying whether one is
much younger or older than the other; but you  may
say, as many have said and think, that the case is very
much altered if the beds which  we are  comparing are 
40
THE PAST CONDITION
continuous.  Suppose two beds of mud  hardened into
rock,—A and B are seen in section.   (Fig. 5.)
   Well, you  say, it is admitted that  the lowermost
bed is always the older.   Very well; B, therefore, is
older  than A.  No doubt, as a whole, it is so; or if
                                         Fig. 5.

any parts of the two beds which are in the same verti-
cal line are compared, it  is so.  But suppose you take
what seems a very natural step further, and  say that
the part a of the bed A is younger than the part b of
the bed B.  Is  this sound reasoning ?   If you find any
record of changes taking place at b, did they occur be-
fore any  events which took  place while a was  being
deposited ?  It  looks all very plain sailing, indeed, to
say that they did;  and  yet there is no proof of any-
thing of the kind.   As the former Director of this In-
stitution,  Sir II. De la  Beche, long ago  showed, this
reasoning may involve an entire fallacy.  It is extremely
possible that a may have been deposited ages before b.
It is very easy to understand how that can  be.  To
return to Fig. 4; when A and B were deposited, they
were  substantially contemporaneous;  A being simply
the finer deposit, and B the coarser of the same detritus
or waste of land.   Now suppose that the sea-bottom
goes down (as shown in Fig. 4), so that the first deposit 
OF ORGANIC NATURE.              41
is carried no farther than a, forming the bed A1, and
the coarse no farther  than b, forming  the bed B1, the
result will  be the formation  of two continuous beds,
one  of fine sediment (AA1)  over-lapping another of
coarse sediment (BB1).   Now suppose  the  whole sea-
bottom is raised up, and  a section exposed about the
point A1;  no doubt, at  this spot, the upper  bed  is
younger  than the lower.  But we should  obviously
greatly err if we concluded that the mass of the upper
bed at A was younger  than  the lower bed at  B;  for
we have just seen that they are contemporaneous  de-
posits. Still more should we be in error if we supposed
the upper  bed at A to  be younger than the continu-
ation of the lowTer bed at B1; for A was deposited long
before B1.   In  fine,  if, instead of  comparing  imme-
diately adjacent parts of two  beds, one of which lies
upon another, we compare distant parts, it is quite pos-
sible that the upper may be any number of years older
than  the under, and  the under any number  of years
younger than the upper.
    Now  you must not suppose that I put this before
you for the purpose of raising a paradoxical difficulty;
the fact is, that the great mass of deposits have taken
place in  sea-bottoms  which are gradually sinking, and
have been formed under the very conditions I am here
supposing.
    Do not run away with the  notion that this subverts
the principle I  laid  down at first.  The error lies  in
extending  a principle which is perfectly applicable to
deposits in the same vertical line to deposits which  are
not in that relation to one another.
    It is  in consequence of circumstances of this kind,
and of others that  I might mention  to you, that our 
42
THE PAST CONDITION
conclusions  on and  interpretations of  the  record are
really and strictly only valid so long as we confine our-
selves  to one vertical section.  I do not  mean to tell
you  that  there are no  qualifying  circumstances,  so
that, even in  very  considerable areas, we may safely
speak of conformably superimposed  beds being older
or younger than others at many different points.  But
we can never be quite  sure in coming to that  con-
clusion, and especially we  cannot  be sure if  there is
any  break  in their continuity, or any very  great dis-
tance between the points to  be compared.
   Well now, so much for the  record  itself,—so much
for its imperfections,—so  much for the conditions to be
observed in interpreting it, and its chronological indi-
cations, the moment  we pass beyond the limits  of a
vertical linear section.
   Now let  us pass from the record  to that which it
contains,—from the  book itself to the writing and the
figures on its pages.  This  writing  and  these figures
consist of remains of  animals and plants which, in the
great majority of cases, have lived and  died in the  very
spot in which we now find them, or at least in the im-
mediate vicinity.  You must all of  you be aware—
and  I  referred to the fact in last  Monday's lecture—
that there are vast  numbers of  creatures living at the
bottom  of the sea.   These creatures, like  all others,
sooner or later die, and their shells and hard parts lie
at the  bottom;  and then the fine mud which is beino-
constantly brought down by rivers  and the  action of
the wear and tear  of the sea, covers  them over and
protects them from  any  further change or  alteration;
and, of course, as in process of time the mud becomes
hardened and solidified, the shells of these animals are 
OF ORGANIC NATURE.
43
preserved and  firmly imbedded  in  the  limestone  or
sandstone which is  being thus formed.  You may see
in the galleries of the Museum upstairs  specimens  of
limestones in which  such fossil  remains of existing
animals are imbedded.   There are some  specimens  in
which turtle's eggs have been imbedded in calcareous
sand, and before the sun had hatched the young turtles,
they  became covered over with calcareous mud, and
thus have been preserved and fossilized.
   Not only does this process  of imbedding and fos-
silization occur with marine and other aquatic animals
and  plants, but it affects those land animals and plants
which are drifted away to sea, or become buried  in
bogs  or morasses;  and the animals  which have been
trodden down by their fellows and crushed in the mud
at the river's bank, as  the herd  have come  to drink.
In any of these cases, the organisms may be crushed
or be mutilated, before or after putrefaction, in such a
manner that perhaps only  a part will be left in  the
form in which  it reaches us.  It is,  indeed, a most  re-
markable fact, that it is quite  an exceptional case to
find a skeleton  of any one of all the  thousands of wild
land  animals that we know are constantly being kill-
ed, or dying in the course of nature : they are preyed
on  and devoured by other animals, or die in places
where their bodies are  not afterwards protected   by
mud.  There are other  animals existing in the sea, the
shells of which form exceedingly  large deposits.  You
are probably aware that before the  attempt was made
to lay the Atlantic  telegraphic  cable, the  Government
employed vessels in making a series of very careful ob-
servations and soundings of the bottom of the Atlantic;
and  although,  as we must  all  regret,  that up  to  the 
44
THE PAST CONDITION
present time that project has not succeeded, we have
the satisfaction of knowing  that it yielded  some most
remarkable  results to science.  The Atlantic Ocean
had  to be  sounded right across, to  depths  of  several
miles in some places, and the nature of its bottom was
carefully ascertained.  Well, now,  a  space of about
1,000 miles wide from east  to west, and I do not ex-
actly know how many from  north  to south, but at any
rate 600 or 700 miles, was  carefully examined, and it
was found that over the whole of that immense area
an excessively fine chalky mud is being deposited ; and
this deposit is entirely made up of animals whose hard
parts are deposited  in this  part of the ocean, and are
doubtless gradually acquiring solidity  and becoming
metamorphosed into a  chalky limestone.   Thus, you
see, it is quite  possible in this way to preserve unmis-
takable records of animal and vegetable life.   When-
ever  the sea-bottom, by  some of those undulations of
the earth's crust that I have referred to, becomes up-
heaved, and  sections or  borings are made, or pits are
dug, then we become able to examine the contents and
constituents of these ancient sea-bottoms, and find out
what manner of animals lived at that period.
   Now it is a very important consideration in its bear-
ing on the completeness  of the record, to inquire how
far the remains contained in these fossiliferous lime-
stones are  able  to convey anything like an accurate
or complete account of the  animals which were in ex-
istence at the time of its  formation.  Upon that point
we can form a very clear judgment, and one in which
there is no possible room for any mistake.   There are
of course a great number of animals—such as jelly-
fishes, and  other  animals—without any  hard parts, 
OF ORGANIC NATURE.
45
of which we  cannot reasonably expect to find any
traces whatever:  there is nothing of them to preserve.
Within  a very short time, you will have noticed, after
they are removed from the water, they dry  up to a
mere  nothing; certainly they are not of a nature  to
leave  any very visible traces of their existence on such
bodies as chalk or mud.  Then again,  look at land ani-
mals ; it is, as I have said, a very uncommon  thing  to
find a land animal  entire after  death.  Insects and
other  carnivorous animals  very speedily pull them  to
pieces, putrefaction takes place, and so, out of the hun-
dreds  of thousands that are known to die every year,
it is the rarest thing in the world  to see one imbedded
in such  a way that  its remains would be preserved for
a lengthened period.   Not only is this the case, but
even when animal remains have been safely imbedded,
certain natural agents may wholly destroy and remove
them.
   Almost all the  hard parts of animals—the  bones
and so on—are composed  chiefly  of phosphate of lime
and carbonate of lime.  Some years ago, I had to make
an inquiry into the  nature of some very curious fossils
sent to  me from  the North of Scotland.  Fossils are
usually  hard bony structures that have become imbed-
ded in  the way I have described, and  have gradually
acquired the nature  and  solidity of  the  body with
which they are associated; but  in this case I had a
series  of holes in some pieces of rock, and nothing else.
Those holes,  however, had a certain  definite  shape
about them, and  when I got a skilful workman to make
castings of the interior of these holes, I found that they
were the impressions of the joints of a back-bone and
of the armour of a  great  reptile, twelve or more feet 
46
THE PAST CONDITION
 long.   This great beast had died and got buried in the
 sand, the sand had gradually hardened over the bones,
 but remained porous.   Water had trickled through it,
 and that water being probably charged with a super-
 fluity of carbonic acid, had dissolved all the phosphate'
 and carbonate of lime, and  the bones themselves had
 thus decayed  and  entirely disappeared; but  as  the
 sandstone happened to have consolidated by that time,
 the precise shape of the bones was retained.  If that
 sandstone had remained  soft a little longer, we should
 have known nothing whatsoever of the existence of the
 reptile  whose bones it had encased.
    How  certain it is  that a vast number of animals
 which  have  existed at one period on  this earth have
 entirely perished, and left no trace whatever of their
 forms, may be proved to you by other considerations.
 There are large tracts of sandstone  in various parts of
 the world, in  which no body has  yet  found anything
 but footsteps.   Not a  bone of any description,  but an
 enormous number of traces of footsteps.   There is no
 question about them.  There is a whole valley in Con-
 necticut covered with these footsteps, and  not a single
 fragment  of the  animals which  made  them have yet
 been found.  Let me mention another case while upon
 that matter, which is even more surprising than those
 to which  I have  yet  referred.  There is a limestone
 formation near Oxford, at a place called Stonesfield,.
 which has yielded the remains of certain very inter-
 esting mammalian  animals, and up to this time, if I
 recollect rightly,  there have  been  found seven  speci-
 mens of its lower jaws, and not a bit of anything else,
neither  limb-bones  nor skull, or any part whatever;
not a ■ fragment of the whole system!  Of course, it 
OF ORGANIC NATURE.
47
 would be preposterous to imagine that the beasts had
 nothing else but a lower jaw !  The probability is, as
 Dr. Buckland showed, as the  result of his observations
 on dead dogs in the river Thames, that the  lower jaw,
 not being secured by very  firm ligaments to the bones
 of the head, and being  a  weighty affair, would easily
 be knocked off, or might drop away from the body as
 it floated in water in a state of decomposition.  The
 jaw would thus be  deposited immediately, while the
 rest of the body would float and drift  away altogether,
 ultimately reaching the  sea, and perhaps becoming de-
 stroyed.   The jaw becomes covered up and preserved
 in  the river  silt, and thus it  comes that we have such
 a curious circumstance  as that of the lower  jaws  in
 the Stonesfield slates.  So  that, you see, faulty as these
 layers of stone in the  earth's crust are, defective as they
 necessarily are as a record, the account of contempora-
 neous vital phenomena  presented by them  is, by the
 necessity of the case, infinitely more defective and frag-
 mentary.
    It was necessary  that  I should put  all this very
 strongly  before you,  because,  otherwise, you might
 have been led to think  differently of the completeness
 of our knowledge by the next  facts I shall state to you.
    The researches of the last three-quarters of a century
 have, in  truth, revealed a wonderful richness of organic
 life in those rocks.  Certainly  not fewer than thirty or
 forty thousand different species of fossils have been dis-
 covered.   You have no more ground for doubting that
 these creatures really lived and  died  at or near the
 places in which we find them than you have for  like
scepticism about a shell on the sea-shore. The evidence
is as good in the one case as in the other. 
48
THE PAST CONDITION
   Our next business is to look at  the general charac-
ter of these fossil remains, and it is a subject which will
be requisite  to consider carefully; and the first point
for us is to examine how much the extinct Flora and
Fauna as  a whole—disregarding altogether the succes-
sion of their constituents, of which I shall speak after-
wards—differ from the Flora and Fauna of the present
day;—how far they differ  in what we do  know about
them, leaving altogether out of consideration specula-
tions based on what we do not know.
   I strongly imagine that if it were not for the rjecu-
liar appearance that fossilized animals have, that any
of you might readily walk through  a museum which
contains fossil remains mixed up with those of the pres-
ent forms  of life, and I doubt very much whether your
uninstructed eyes would lead you  to see  any vast or
wonderful difference between the two.  If you  looked
closely, you would notice, in the first place, a great
many things very like animals with which  you are
acquainted now: you would see differences of shape
and proportion, but on the whole a close similarity.
   I explained what I meant by Orders the other day,
when I described the animal kingdom as being divided
into sub-kingdoms, classes, and orders.  If you  divide
the animal kingdom  into orders,  you will  find  that
there are above one hundred and  twenty.  The num-
ber may vary on one side  or  the  other, but this is a
fair estimate. That is  the sum total of the orders of
all the animals which we know now, and which have
been known in past times, and left remains behind.
   Now, how many of those  are  absolutely extinct?
That is to say, how many of these orders of animals
have lived at a former period of the world's history, 
OF ORGANIC NATURE.
49
 but have at present no representatives?  That  is the
 sense in which I meant to use the word " extinct."  I
 mean that those animals did  live on th'is  earth at one
 time, but have left no one  of their kind with us at the
 present moment.  So that estimating the number of
 extinct animals is a sort of way of  comparing the past
 creation as a whole with the present as a whole.  To
 make  that  clear, I have written in red ink  on  these
 diagrams the names of all those extinct orders, and in
 black ink the names of the rest.  Among the mammalia
 and birds there  are none  extinct;  but when we  come
 to the reptiles there is a most  wonderful thing: out of
 the eight orders, or thereabouts, which you can  make
 among  reptiles, one-half are extinct.   These diagrams
 of the plesiosaurus, the ichthyosaurus, the pterodactyle,
 give you a notion of some of  these extinct  reptiles.
 And here is the cast of the pterodactyle and bones of
 the ichthyosaurus and the plesiosaurus, just as fresh as
 if it had been recently dug up in a churchyard.  Thus,
 in the reptile class, there are no less than half of the
 orders which are absolutely extinct.  If we turn to the
 Amphibia, there was one extinct order, the  Labyrintho-
 donts, typified by the large salamander-like beast shown
 in this diagram.
   No order of fishes  is known  to be extinct.  Every
 fish that we find in the strata—to which I have  been
 referring—can  be identified and  placed in one of the
 orders which  exist  at  the  present day.  There is not
 known  to be a  single ordinal form of insect  extinct.
 There are only two orders extinct among the Crustacea.
 There is not known  to be an extinct order of these  crea-
tures, the parasitic and other worms ; but there are two,
not to say three, absolutely extinct orders of this class,
        3 
50
THE PAST CONDITION
the Fchinodermata ; out of all the orders of the Coden-
terata and Protozoa only one, the Rugose  Corals.
   So that, you see, out of somewhere about 120 orders
of animals, taking them altogether, you will not, at the
outside  estimate, find  above ten  or  a dozen extinct.
Summing up all the order of  animals which have left
remains behind  them,  you will not find above  ten or
a dozen which cannot  be arranged with  those  of the
present  day;  that is to say,  that the difference does
not amount to much more than ten per cent.; and the
proportion of extinct orders of plants is  still smaller.
I think that that is a very astounding, a most astonish-
ing fact, seeing  the  enormous epochs of time  which
have elapsed during the constitution of the surface of
the earth  as it at present exists;  it is, indeed, a most
astounding thing that the proportion of extinct ordinal
types should be so exceedingly small.
   But  now, there is  another point of view in  which
we must look at this past creation.   Suppose that we
were to sink a vertical pit  through  the floor beneath
us, and that I could  succeed in making a section right
through in the direction of  New Zealand,  I should find
in each of the different beds  through which I passed
the remains  of  animals which I  should  find in that
stratum and not in  the  others.   First, I  should come
upon beds of gravel or drift  containing the bones of
large  animals, such  as the elephant,  rhinoceros,  and
cave tiger.  Rather curious things  to fall  across in
Piccadilly !   If I should dig lower still, I should come
upon a  bed of what we  call the  London  clay, and in
this, as you will see in our galleries up-stairs,  are found
remains of strange cattle, remains of turtles, palms, and
large tropical fruits;  with shell-fish such as you see the 
OF ORGANIC NATURE.
51
like of now only in tropical regions.  If I went below
that, I should come upon the chalk, and there I should
find something  altogether different,  the  remains  of
ichthyosauri  and pterodactyles, and  ammonites, and
so forth.
    I do not know what Mr. Godwin Austin would say
comes  next, but probably rocks containing more am-
monites, and more ichthyosauri and  plesiosauri, with
a vast number of other things ; and under that I should
meet with yet older rocks, containing numbers of strange
shells and fishes ; and in thus passing from the surface
to the lowest depths of the earth's crust, the forms  of
animal life and vegetable life which I should meet with
in the successive beds would, looking at them broadly,
be the more different the further that I went down.
Or, in  other words, inasmuch gs we  started  with the
clear principle, that in a series of naturally-disposed
mud beds the lowest are the oldest,  we should come
to this  result, that the further we  go back in time the
more difference  exists between the animal and vege-
table life of an epoch and that which now exists.  That
was the conclusion to which I wished  to bring you  at
the end of this Lecture. 
LECTURE  HI.
 THE METHOD BY WHICH THE CAUSES OF THE PRES-
     ENT AND PAST CONDITIONS OF ORGANIC NATURE
     ARE TO BE DISCOVERED.—THE ORIGINATION OF
     LIVING BEINGS.

    In the two preceding lectures I have endeavoured
 to indicate to you the extent of  the subject-matter of
 the  inquiry upon which we are engaged; and  now,
. having thus acquired some conception of the Past and
 Present phenomena of Organic Nature, I must turn, to-
 night, to that which constitutes the great problem which
 we  have set before ourselves;—I mean, the  question
 of what knowledge we have of the causes  of  these
 phenomena of organic  nature,  and  how such knowl-
 edge is obtainable.
   Here, on the  threshold of  inquiry, an objection
 meets us.   There  are in  the world  a number of ex-
 tremely  worthy,  well-meaning  persons, whose judg-
 ments and opinions are entitled  to the utmost respect
 on account of their sincerity, who are of opinion that
 Yital Phenomena, and especially  all  questions  relating
 to the origin of vital phenomena, are questions quite
 apart from  the ordinary run  of  inquiry, and  are, by
 their very nature, placed  out  of our  reach. They say 
METHOD OF DISCOVERY.
53
 that all these phenomena originated  miraculously, or
 in some way totally different from the ordinary course
 of nature, and that therefore they conceive it  to  be
 futile, not to  say presumptuous, to attempt  to inquire
 into them.
    To  such sincere  and earnest persons, I would only
 say, that a question  of this kind is not  to  be shelved
 upon theoretical or speculative  grounds.    You  may
 remember the story of the Sophist who demonstrated
 to Diogenes in the most complete and satisfactory man-
 ner  that  he could  not walk; that, in fact,  all motion
 was an impossibility ; and that Diogenes refuted him
 by simply getting up and walking round his tub. So,
 in the same way, the  man of science replies to objec-
 tions of this kind,  by simply getting  up and walking
 onward, and  showing  what science has  done and  is
 doing,—by  pointing to that  immense mass of facts
 which have been ascertained and systematized under the
 forms of the great doctrines of Morphology, of Develop-
 ment, of Distribution, and the like.  He sees an enor-
 mous mass of facts and laws relating to organic beings,
 which stand  on the same good sound foundation  as
 every other natural law ; and, therefore, with this mass
 of facts and laws before us, seeing that, as far as organic
 matters have hitherto been accessible and studied, they
 have shown themselves capable of yielding to scientific
 investigation, we may accept this  as proof that order
 and  law reign  there as well as in the rest of nature;
 and  the man of science says nothing  to objectors of
 this  sort, but  supposes that we can and shall walk to
 the origin of organic nature, in the same way that we
 have walked to a knowledge of the laws and  Drinciples
of the inorganic world. 
54
METHOD  OF DISCOVERY.
   But  there  are objectors who say  the  same from
ignorance and  ill-will.  To such I would reply that the
objection comes  ill  from them, and that the real pre-
sumption, I may almost say the real blasphemy, in this
matter, is in the attempt to limit that inquiry into the
causes of phenomena which is the source of all human
blessings, and  from which has sprung all human pros-
perity and progress; for, after all, we  can  accomplish
comparatively little; the limited range  of  our own
faculties  bounds us on every side,—the  field of  our
powers of observation is small enough, and he who en-
deavours  to narrow the sphere of our inquiries is only
pursuing a course that is likely to produce the greatest
harm to his fellow-men.
   But now, assuming, as we all do, I hope, that these
phenomena are properly accessible to inquiry, and  set-
ting out upon our search into the causes of the phe-
nomena of organic nature, or, at any rate, setting out to
discover  how  much wTe at  present know  upon these
abstruse  matters, the question  arises as to what is to be
our  course of proceeding, and what method  we must
lay down for our guidance.   I reply to that  question,
that our  method must be  exactly the same as that
which is  pursued in any other scientific  inquiry, the
method of scientific investigation being the  same for
all orders of facts and phenomena whatsoever.
   I must dwell a little on this point, for I  wish you
to leave  this room with a very clear  conviction that
scientific investigation  is not, as many people seem to
suppose,  some kind  of modern black art.  I say that
you  might easily gather this impressson from the man-
ner in which many persons  speak of scientific inquiry,
or talk  about  inductive and  deductive philosophy, or 
METHOD OF DISCOVERY.
55
the  principles  of  the  " Baconian philosophy."  I do
protest that, of the vast number of cants in this world,
there are none, to my mind, so  contemptible as the
pseudo-scientific cant which is talked  about  the " Ba-
conian philosophy."
    To hear people talk about the great Chancellor,-^
and a very great man he certainly was,—you would
think  that it was  he who had invented science,  and
that there was no such thing as sound reasoning before
the  time of Queen Elizabeth!   Of course,  you say,
that cannot possibly be true; you perceive,  on a  mo-
ment's reflection, that such an idea is absurdly wrong;
and yet, so firmly  rooted is this sort of impression,—I
cannot call it an idea, or conception,—the thing is too
absurd  to be entertained,—but so completely  does  it
exist at  the bottom of most men's minds, that this has
been a matter of observation with me for many years
past.  There are many men who, though knowing ab-
solutely  nothing of the subject with which  they may
be dealing, wish,  nevertheless, to damage the author
of some view with which they think fit to disagree.
What they do, then, is not to go and learn something
about the subject, which one would naturally  think the
best way of fairly dealing with it; but they abuse the
originator of the view they question, in a general man-
ner, and wind up by saying that, "  After all, you know,
the principles and method of this author are  totally
opposed  to the  canons  of the Baconian  philosophy."
Then everybody applauds, as  a matter of course, and
agrees that  it must be so.  But if you were to stop
them all in the middle of their applause, you would
probably  find  that neither the speaker nor his  ap-
plauders could tell you how or in what way it was so ; 
56
METHOD OF DISCOVERY.
neither  the one nor the other having the slightest idea
of what they mean when they speak of the " Baconian
philosophy."
   You will  understand, I hope, that  I  have not the
slightest desire to join in the outcry against either the
morals, the intellect, or the great genius of Lord Chan-
cellor Bacon.  He was undoubtedly a very great man,
let people  say what  they will of  him ; but notwith-
standing all  that he  did for philosophy, it would  be
entirely wrong to suppose that the methods of modern
scientific inquiry originated with him, or with his age;
they originated with  the first man, whoever he was;
and  indeed existed long before him, for many of the
essential processes  of reasoning are exerted by  the
higher order of brutes as completely and effectively as
by ourselves.  We see in many of the brute creation
the exercise  of one, at least, of the same powers  of
reasoning as that which we ourselves employ.
   The  method  of scientific investigation is nothing
but the expression  of  the necessary mode of working
of the human mind.   It is simply the mode at which
all phenomena are reasoned about, rendered  precise
and  exact.   There is  no more difference, but there is
just  the same kind of difference, between the  mental
operations of a man of science and those of an ordinary
person, as there is between the operations and methods
of a baker or of a butcher weighing out his goods in com-
mon  scales, and the operations of a chemist in perform-
ing a difficult and  complex analysis by means  of his
balance  and finely-graduated weights.   It is not that
the action of the scales in the one case, and the balance
in the other, differ in  the principles of their construc-
tion or manner of working ;  but the beam of one is set 
               METHOD OF DISCOVERY.              57

on an infinitely finer axis than the other, and of course
turns by the addition of a much smaller weight.
   You will understand this better, perhaps, if I give
you  some familiar example.  You have all heard it re-
peated, I dare say," that men of science work by means
of Induction and Deduction, and that by the help of
these operations, they, in a sort of sense, wring from
Nature certain other things, which are called Natural
Laws, and Causes, and  that out of these, by some cun-
ning skill of their own, they build up Hypotheses  and
Theories. And it is imagined by many, that the opera-
tions of the common mind can be by no means com-
pared with  these processes, and that they have to be
acquired by a sort of special apprenticeship to the craft.
To hear all these large words, you would think  that
the mind of a man of science must be constituted dif-
ferently from  that of his fellow-men ; but if you  will
not  be frightened by terms, you will discover that you
are quite wrong, and that all these terrible apparatus
are being used by yourselves every day and every hour
of your lives.
   There is a well-known incident in one of Moliere's
plays, where the  author makes  the hero express un-
bounded delight on  being told that he had been talk-
ing  prose during the  whole  of his life.   In the same
way, I trust,  that you wTill take comfort, and be de-
lighted  with  yourselves, on  the discovery  that  you
have been acting on  the principles of inductive  and
deductive philosophy  during the same period.  Prob-
ably there is  not one  here to-night who has not in the
course of the day had  occasion to set in motion a com-
plex train of reasoning, of the very same kind, though
differing of course in degree, as that which a scientific
         3* 
58
METHOD  OF DISCOVERY.
man goes through in tracing the causes of natural phe-
nomena.
   A very trivial circumstance will serve to exemplify
this.  Suppose you go into a fruiterer's shop, wanting
an apple,—you take up one, and, on biting it, you find
it is sour ; you look  at it, and see that it is hard and
green.  You take up another one, and that too is hard,
green, and  sour.  The shopman offers  you a third;
but, before biting it, you examine it, and find that it is
hard  and green, and  you immediately  say that you
will not have it,  as it must be sour, like those that you
have already tried.
   Nothing can be more simple than that, you think;
but if you will  take the trouble to analyze and trace
out into its logical elements what  has  been done  by
the mind, you will be greatly  surprised.  In  the first
place, you have performed  the  operation  of Induc-
tion.   You  found  that, in two experiences, hardness
and greenness in apples go together with  sourness.  It
was so in the first case, and it was confirmed by the
second.  True, it is  a very small  basis, but still it is
enough to make an  induction from ; you generalize
the facts, and you expect to find  sourness  in apples
where you  get  hardness and  greenness.  You found
upon that a general law, that all hard and green apples
are sour; and that, so far as it goes, is a  perfect induc-
tion.   Well, having  got your natural law in this way,
when you  are offered  another  apple which  you find is
hard  and  green, you say, " All hard and green apples
are sour;  this apple is hard and green, therefore this
apple  is sour."  That train of reasoning  is what logi-
cians call  a syllogism, and has all its various  parts and
terms,—its major  premiss, its minor premiss, and its 
METHOD  OF DISCOVERY.
59
 conclusion.   And, by the help of further reasoning,
 which, if drawn out, would have to be  exhibited in
 two or three other syllogisms, you arrive  at your final
 determination, " I will not have that apple."  So that,
 you see, you have, in the first place, established a law
 by Induction, and upon that you  have founded a De-
 duction, and reasoned out the special conclusion of the
 particular case.  Well now, suppose, having got your
 law, that at  some time afterwards, you are discussing
 the qualities of apples with a friend : you will say to
 him, "It is  a very curious thing,—but  I  find that all
 hard  and green apples are sour!"  Your friend says
 to you, " But how do you know that ? "  You at once
 reply,  " Oh,  because I have tried it over  and over
 again, and have always found them to be so."  Well,
 if we were talking science instead of common sense, we
 should call that an Experimental Verification.  And, if
 still opposed, you go further, and  say, " I have heard
 from  the people  in Somersetshire and  Devonshire,
 where a large number of apples are grown, that they
 have observed the same thing.  It is also found to be
 the case in  Normandy,  and  in North America.  In
 short, I find it to be the universal experience of man-
 kind wherever  attention has been directed to the sub-
 ject."   Whereupon, your friend, unless he is  a very
 unreasonable man, agrees with you, and is  convinced
 that you are quite  right  in the conclusion you have
 drawn.   He  believes, although  perhaps he  does  not
 know he believes it, that the more extensive Verifica-
 tions are,—that the more frequently experiments have
 been made, and results of the same kind arrived at,—
that the more varied the  conditions under which the
same results  have been attained, the more certain is 
60
METHOD OF DISCOVERY.
the ultimate  conclusion, and he disputes the question
no further.   He  sees  that  the  experiment  has been
tried under all sorts of conditions, as  to time, place,
and people, with the same result;  and he says with
you, therefore, that the law you have lafd down must
be a good one, and he must believe it.
   In science we  do the same thing;—the philosopher
exercises precisely the same faculties, though in a much
more delicate manner.   In scientific inquiry it becomes
a matter of  duty to expose  a supposed law to even-
possible kind of  verification, and  to take care, more-
over, that this is done intentionally, and not  left to a
mere  accident, as in the case of the apjjles.  And in
science, as  in common life, our confidence in a law is
in exact proportion to the absence  of variation  in the
result of our  experimental verifications.   For instance,
if you let go your grasp of an article you may have in
your hand, it  will  immediately fall to the ground.  That
is a very common verification of one of the best estab-
lished laws of nature—that of gravitation. The method
by which men of science establish the existence of that
law is exactly the same as that by which w7e have estab-
lished the trivial proposition about the sourness of hard
and green apples.  But we believe it in  such an exten-
sive, thorough, and unhesitating  manner because the
universal experience of mankind verifies it, and we can
verify it ourselves at any time; and that  is the strongest
possible foundation on which any natural law can rest.
   So much by way of proof that the method of estab-
lishing laws in science is exactly the same as that pur-
sued in common life.    Let  us  now turn to another
matter (though really  it is but another phase  of the
same question), and that is, the method by which, from 
METHOD OF DISCOVERY.
61
 the relations of certain phenomena, we prove that some
 stand in the position of causes towards the others.
    I want to put the case clearly before you, and I will
 therefore show you what I mean by another familiar
 example.  I will suppose that  one of you, on coming
 down in the morning to the parlour of your house, finds
 that a tea-pot and some spoons  which  had been left in
 the room on the previous evening are  gone,—the win-
 dow is open, and you observe the mark of a dirty hand
 on the window-frame, and perhaps, in  addition to that,
 you notice the  impress  of a hob-nailed shoe on the
 gravel .outside.  All these phenomena have struck your
 attention instantly, and before two minutes have passed
 you say, " Oh, somebody has broken open the  window,
 entered the room, and run off with the spoons and the
 tea-pot! "  That speech is out of your mouth  in a mo-
 ment.   And  you will probably add,  " I know there
 has ; I am quite sure of it! " You mean to say exactly
 what you know ; but in reality what you have said has
 been the expression of what is, in all essential particu-
 lars, a Hypothesis.  You do not know it at all; it is
 nothing  but  a hypothesis rapidly framed  in your own
 mind!  And it is a hypothesis founded on a long train
 of inductions and deductions.
   -What are those inductions and deductions, and how
 have you got at  this hypothesis ?  You have observed,
 in the  first place, that the window is open ; but by a
 train of reasoning involving many Inductions and De-
 ductions, you have probably arrived long  before at the
 General Law—and a very good one it is—that windows
 do not open of themselves ; and you therefore conclude
 that something  has opened  the window.  A second
general law that you have arrived at in the same way 
62             METHOD OF DISCOVERY.
is, that tea-pots and spoons do not go out of a window
spontaneously, and you  are satisfied  that, as they are
not now where you left them, they have been removed.
In the third  place, you look at the marks on the win-
dow-sill, and the shoe-marks outside, and you say that
in all previous experience the  former kind of mark
has never been  produced by anything else  but the
hand of a human being;  and the same experience shows
that no other animal but man at present wears shoes
with hob-nails on them such  as would produce the
marks in the gravel.  I  do not know, even if we could
discover any of those " missing  links " that  are talked
about, that they would help us to any other conclusion!
At any rate the law which states our present experience
is strong enough for my present purpose.   You next
reach the conclusion, that as these kinds of marks have
not been left  by any  other animals than men, or are
liable to be formed in any other way than by a man's
hand and shoe, the marks in question have been formed
by a man in that way.  You have, further, a  general
law, founded on observation and experience, and that,
too, is,  I am sorry to say, a very universal and unim-
peachable one,—that some men are thieves; and you
assume at once from all these  premisses—and  that  is
what constitutes your hypothesis—that  the  man who
made the marks outside and on the window-sill, opened
the window, got into the room,  and stole your tea-pot
and spoons.  You have now arrived at a Vera  Causa ;
—you have assumed a Cause which it is plain  is com-
petent to produce all the phenomena you have observed.
You can explain all these phenomena only by  the hy-
pothesis of a thief.  But that is a hypothetical  conclu-
sion, of the justice of which you have no absolute proof 
METHOD OF DISCOVERY.
63
 at all; it is only rendered  highly probable by a series
 of inductive and deductive reasonings.
    I suppose your first action, assuming you are a man
 of  ordinary common sense, and that you have estab-
 lished this hypothesis to  your own satisfaction,  will
 very likely be to go off for the police, and set them on
 the track of the burglar, with the view to the recovery
 of  your property.   But just as you are starting with
 this object, some person comes in, and on learning what
 you are  about, says, " My  good friend, you are going
 on  a great  deal too fast.  How do you  know that the
 man who really made the marks took the spoons ?  It
 might have been a monkey that  took  them, and the
 man may  have merely  looked  in afterwards."  You
 would probably  reply, " Well, that is  all very well,
 but you  see it is contrary to  all experience of the way
 tea-pots  and spoons are abstracted; so that, at any rate,
 your hypothesis is  less probable  than mine."  While
 you are talking  the thing over in this  way, another
 friend arrives,  one  of  that good kind of people that I
 was talking of  a little while ago.   And  he might say,
 " Oh, my dear sir, you are certainly going on  a great
 deal too  fast.  You are most presumptuous.  You ad-
 mit that all these  occurrences took place when you
 were fast asleep, at  a time when you could not possibly
 have  known anything about what was  taking place.
 How do  you know that the laws of Nature are not sus-
 pended  during the night ?   It  may be that  there has
 been some kind  of supernatural interference in this
 case."  In  point of fact, he declares that  your hypoth-
esis is one of which you cannot at all demonstrate the
truth, and  that you are by  no means  sure  that  the 
64
METHOD OF DISCOVERY.
 laws of Nature are the same when you are asleep as
 when you are awake.
    Well, now, you cannot at the moment  answer that
 kind of reasoning.  You feel that your worthy friend
 has you somewhat at a disadvantage.   You will feel
 perfectly convinced  in  your own  mind, however, that
 you  are  quite right, and you say to him, " My good
 friend, I  can only be guided by the natural probabili-
 ties of the case, and if you will be kind enough to stand
 aside  and permit me to pass, I will go and fetch the
 police."  Well, we will suppose  that your journey is
 successful, and  that  by good  luck you meet with a
 policeman; that eventually  the burglar is  found with
 your property on his person, and the marks correspond
 to his hand and to his boots.  Probably any  jury would
 consider those facts a very good experimental verifica-
 tion of your  hypothesis, touching the cause of the ab-
 normal phenomena observed in your parlour, and would
 act accordingly.
    Now, in this supposititious case I have taken phe-
 nomena of a very common  kind, in order that you
 might see what are the different steps in an ordinary
 process of reasoning, if you will only take the  trouble
 to analyze it carefully.   All  the operations  I have de-
 scribed, you will see, are involved  in the mind of any
 man of sense in leading him to a conclusion as to  the
 course he should take in order to make good a robbery
 and punish the offender.  I say that  you are led, in
 that case, to your conclusion  by exactly the  same train
 of reasoning  as that which a man of science pursues
when he is endeavouring to discover the origin  and
laws of the most occult phenomena.  The  process is,
and always must be, the same; and precisely the same 
METHOD OF DISCOVERY.
65
 mode of reasoning was employed  by  Newton and
 Laplace in their endeavours to discover and define the
 causes of the movements of the heavenly bodies, as you,
 with your own common sense, would employ to detect
 a burglar.  The only difference is, that the  nature of
 the inquiry being more abstruse, every step has  to be
 most  carefully watched,  so that  there may not be a
 single crack  or flaw in  your hypothesis.  A flaw or
 crack in many of the  hypotheses of daily life  may be
 of little or no nToment as  affecting the general  correct-
 ness  of the  conclusions at which we may arrive; but
 in a scientific inquiry a fallacy, great or small, is always
 of importance, and is sure to be  constantly productive
 of mischievous, if not fatal,  results in the long run.
   Do not allow yourselves to be  misled by the com-
 mon  notion that a hypothesis is  untrustworthy simply
 because it is a hypothesis.   It is often urged, in respect
 to some  scientific conclusion, that, after all, it  is only
 a hypothesis.  But what more have we to guide  us in
 nine-tenths  of the most important affairs of daily life
 than  hypotheses, and  often very ill-based ones?  So
 that  in science, where the  evidence of a  hypothesis is
 subjected to the most rigid examination, we may rightly
 pursue the  same course.  You may have hypotheses
 and hypotheses.  A man may say, if he likes, that the
 moon  is  made of green cheese:  that is a hypothesis.
 But another man, who has devoted a great deal of time
 and attention to the subject, and availed himself of the
 most powerful telescopes and the results of the observa-
 tions  of others, declares  that in his opinion it is prob-
 ably  composed  of materials very similar  to  those  of
which our own earth is made up : and that is also only a
hypothesis.  But I need not tell  you that there is an 
66
METHOD OF DISCOVERY.
enormous difference in the value of the two hypotheses.
That one which is based on  sound scientific knowledge
is sure to have a corresponding value; and  that which
is a mere hasty random guess is likely to have but little
value.   Every great step in our progress in discovering
causes has been made in exactly the same way  as that
which  I have detailed to you.  A person observing the
occurrence of certain facts and phenomena asks, natu-
rally  enough, what process, what  kind  of operation
known to  occur in nature  applied to the particular
case, will unravel  and  explain the mystery?  Hence
you have the scientific hypothesis: and  its value will
be proportionate to the  care  and completeness  with
which  its basis had been tested and verified.  It  is in
these matters as in  the commonest affairs of practical
life: the guess of the fool will be folly, while the guess
of the wise man will contain wisdom.   In all cases,
you see  that  the value  of the result depends  on the
patience and faithfulness with which the investigator
applies to his hypothesis every possible kind of verifi-
cation.
   I dare say I may have to  return to this point by-
and-by;  but having dealt  thus far with our  logical
methods, I must now turn to something which, perhaps,
you may consider  more  interesting, or,  at any  rate,
more tangible.   But in  reality there are but few things
that can be more important for you to understand than
the mental processes and the means by which we obtain
scientific conclusions  and theories.*  Having granted
that the inquiry is a proper one, and having determined

  * Those who wish to  study fully  the doctrines of  which I have en-
deavoured to give some rough and ready illustrations, must read  Mr. John
Stuart Mill's " System of Logic." 
            ORIGINATION OF LIVING BEINGS.         67

 on the nature of the methods we are to pursue and
 wliich only can lead to success, I must now turn to the
 consideration of  our knowledge of the nature of the
 processes which have resulted in the present condition
 of organic nature.
    Here, let me say at once, lest some of you misun-
 derstand  me, that I have  extremely  little to report.
 The question of  how the present condition of organic
 nature  came about, resolves itself into two questions.
 The first is:  How has organic or living matter com-
 menced its existence ?   And the second is : How has it
 been perpetuated?   On  the second question I shall
 have more to say hereafter.   But on the first one, what
 I  now have to say will be for the most part of a nega-
 tive character.
    If you consider what kind of evidence we can have
 upon this  matter, it will  resolve itself into two kinds.
 We may have historical evidence and we may  have ex-
 perimental evidence.  It  is, for example, conceivable,
 that inasmuch as the hardened mud which  forms  a
 considerable portion of the  thickness  of the earth's
 crust contains faithful records  of the past forms of life,
 and inasmuch as these differ more and more as we go
 further  down,—it is  possible and  conceivable that we
 might come to some  particular bed or stratum which
 should  contain the  remains  of  those  creatures  with
 which organic life began upon the earth.  And  if we
 did so,  and  if such  forms  of organic  life were  pre-
 servable, we  should  have what I would call historical
 evidence of the mode in which organic  life began upon
this  planet.  Many persons will tell you,  and indeed
you will find it stated in many works on geology, that
this has been done, and that we  really possess such  a 
68          ORIGINATION OF LIVING BEINGS.

record; there are some who imagine that the earliest
forms of life of which w^e  have as yet discovered  any
records, are in truth the forms in which animal life be-
gan upon the globe.   The grounds on which they base
that supposition are these:—That if you go  through
the enormous thickness of the  earth's crust  and get
down to the older rocks, the higher vertebrate animals
—the quadrupeds, birds, and fishes—cease to be found ;
beneath them you find only the  invertebrate animals;
and in the deepest and lowest  rocks those remains be-
come scantier and  scantier, not in any very gradual
progression, however, until, at length, in what are sup-
posed to be the oldest rocks,  the  animal  remains Avhich
are found are almost  always confined to four forms,—
Oldhamia, whose precise nature is not known, whether
plant, or animal; Lingula, a kind of mollusc ; Trilo-
bites,  a  crustacean animal, having the  same essential
plan of construction, though differing in many details
from  a  lobster or crab ;  and  Hymenocaris, which is
also a crustacean.  So that you have all the Fauna re-
duced, at this period, to four forms : one a kind of ani-
mal or plant  that we know  nothing about, and three
undoubted animals—two crustaceans and one mollusc.
   I think, considering the organization of these mol-
lusca  and Crustacea, and looking at their very complex
nature, that it does indeed require a very strong ima-
gination to conceive that these  were the first  created of
all living things.  And you must take  into considera-
tion the fact that we have not the slightest proof that
these which we call the oldest beds are really so : I re-
peat, we have not the slightest proof of it.   When you
find in some  places that in  an enormous thickness of
rocks  there are but very scanty traces of life, or  abso- 
ORIGINATION OF LIVING  BEINGS.
69
lutely none at all;  and that in other parts of the world
rocks  of the very  same formation are crowded with
the records of living forms ;  I think it is impossible to
place any reliance on the supposition, or to feel oneself
justified in supposing that these are the forms in which
life first commenced.  I have not time here to enter
upon the technical grounds  upon which  I am led  to
this conclusion,—that could hardly be done properly
in half a dozen lectures on  that part alone;—I must
content myself with saying that I do not at all believe
that these are the oldest forms of life.
    I turn to the experimental side to see what evidence
we have there.   To enable us to say that we know any-
thing about the experimental  origination of organiza-
tion and life, the investigator ought to be able to take
inorganic matters, such as carbonic acid, ammonia, wa-
ter, and  salines, in  any sort  of inorganic combination,
and be able to build them up into Protein  matter, and
that that Protein matter ought to begin to live in an
organic form.  That, nobody has done as yet,  and I
suspect it  will be  a long while before anybody does
do it.  But the thing  is by no means so impossible as
it looks ; for the researches of modern chemistry have
shown us—I won't say the  road towards  it, but, if I
may so say, they have shown the finger-post pointing
to the road that may lead to it.
   It is not many  years ago—and you must recollect
that Organic Chemistry is a  young science, not above
a couple of generations old,—you must not expect too
much of  it; it is not many years ago since it was said
to be  perfectly impossible  to fabricate any organic
compound;  that is  to say, any non-mineral compound
which  is to be found in  an organized being. It re- 
70         ORIGINATION OF LIVING BEINGS.
mained so for a very long period ; but it is now a con-
siderable number of years since a distinguished foreign
chemist contrived to fabricate Urea, a substance of a
very complex character, wliich forms one of the waste
products of animal structures.  And of late years a
number of other compounds, such as Butyric Acid,
and others, have been added to the list.   I need not
tell you that chemistry is  an enormous distance from
the goal I  indicate; all  I wish to point out to you is,
that it is by no means safe to say that that goal may
not be reached one day.   It  may  be that it is impos-
sible for us to produce the conditions  requisite to the
origination of life ; but we must speak modestly about
the matter, and recollect that Science has put her foot
upon the bottom round of the ladder.   Truly he would
be a bold man who would venture  to predict where she
will be fifty years hence.
   There is  another  inquiry  which  bears indirectly
upon this question, and upon which I  must say a few
words.  You are all of you aware of  the  phenomena
of what is  called spontaneous generation.   Our fore-
fathers, down to the  seventeenth  century,  or  there-
abouts, all  imagined, in perfectly good faith, that cer-
tain vegetable and animal forms gave birth, in  the
process of their decomposition, to insect life.  Thus, if
you put a  piece of meat in the  sun, and allowed it to
putrefy, they conceived that the grubs which soon be-
gan to appear were the result of the action  of a power
of spontaneous generation which the  meat contained.
And they could give  you receipts for  making various
animal and vegetable  preparations which  would pro-
duce particular kinds of animals.  A very distinguish-
ed Italian  naturalist,  named  Eedi, took  up the ques- 
            ORIGINATION OF LIVING  BEINGS.         71

 tion, at a time when everybody believed in it; anions
 others our own great  Harvey, the discoverer of the
 circulation of the  blood.   You will constantly find his
 name quoted, however, as  an  opponent of the doctrine
 of spontaneous  generation; but the fact is,  and you
 will see it if you will take the trouble to look into his
 works, Harvey  believed it as profoundly as any man
 of his time;  but he happened to enunciate a very cu-
 rious proposition—that every living thing came from
 an egg ;  he did  not mean to use the word in the  sense
 in which we now  employ it, lie only meant to say that
 every living thing originated in a  little rounded par-
 ticle of organized substance; and  it is from  this cir-
 cumstance, probably, that  the notion of Harvey having
 opposed the  doctrine originated.  Then came Eedi,
 and he proceeded to upset the doctrine  in a very simple
 manner.  He merely covered the piece of meat with
 some very fine  gauze, and then he exposed it to the
 same conditions.  The result of this was that no grubs
 or insects were produced; he proved  that the grubs
 originated  from the insects who came and deposited
 their eggs  in the  meat, and  that  they were  hatched
 by the  heat of  the  sun.  By this kind of inquiry he
 thoroughly upset the doctrine of spontaneous genera-
 tion, for his time at least.
    Then came the discovery and  application of the
 microscope  to scientific inquiries,  which  showed to
 naturalists  that besides the  organisms which  they
 already knew as living beings and  plants, there were
 an immense number of minute things which could be
 obtained apparently almost at will from  decaying vege-
table and animal  forms.   Thus, if  you took some or-
dinary black pepper or some  hay,  and steeped it in 
72          ORIGINATION OF LIVING BEINGS.

water, you would find in the course of a few days that
the water  had become impregnated with an  immense
number of animalcules  swimming about in all direc-
tions.  From facts of this kind  naturalists were led to
revive the theory of spontaneous  generation.  They
were headed here by an English naturalist,—Needham,
—and afterwards in  France by  the  learned Buffon.
They  said  that these things were absolutely  begotten
in the water of the decaying substances out of which
the infusion was made.  It did not matter whether you
took animal or vegetable matter, you had only to steep
it  in  water  and  expose it, and you would soon have
plenty of animalcules.   They made  a hypothesis about
this which was a very fair one.  They said, this matter
of the animal wrorld, or of the higher plants, appears to
be dead, but in reality it has a sort of dim life about it,
which, if it is placed under fair conditions, will cause it
to break up into  the forms of these little animalcules,
and they will go  through their lives  in the same way as
the animal or plant of which they  once formed a part.
   The  question now  became very hotly  debated.
Spallanzani, an  Italian naturalist,  took up  opposite
views to those of Needham  and Buffon, and by means
of certain experiments he showed that it was quite pos-
sible to stop the process by boiling the water, and clos-
ing the vessel in wliich it was contained.  " Oh ! " said
his opponents; " but what do you  know you may be
doing when you heat the air over the water in this way ?
You may be destroying  some property of the air requi-
site for the spontaneous generation of the animalcules."
   However, Spallanzani's  views were supposed  to  be
upon  the right  side, and those  of the others fell into
discredit;  although the fact was that  Spallanzani had 
           ORIGINATION OF LIVING BEINGS.          73

not made good his views.   Well, then, the subject con-
tinued to be revived from time to time, and experiments
were made by several persons; but these experiments
were not altogether satisfactory.  It was found that if
you put an infusion in which animalcules would appear
if it were exposed to the air  into a vessel and boiled
it, and then sealed up the mouth of the vessel, so that
no  air, save  such as had  been heated  to  212°, could
reach its contents, that then no animalcules would be
found; but if you took the same vessel and exposed
the infusion to the air, then you would get animalcules.
Furthermore, it was  found that if you connected the
mouth of the vessel with a red-hot  tube in such a way
that the  air would have to  pass through  the tube  be-
fore reaching the infusion, that  then you would get
no  animalcules.   Yet another thing was noticed: if
you took two flasks  containing the same kind of infu-
sion, and left one entirely exposed to the air, and in
the mouth  of the other placed a ball of cotton wool,
so  that  the  air would  have to filter itself through it
before reaching the infusion,  that then, although  you
might have plenty of animalcules in the first flask, you
would certainly obtain none from the second.
    These experiments, you sec, all tended towards one
conclusion—that the infusoria were developed from little
minute spores or  eggs which were constantly floating
in  the atmosphere,  which lose their power of germi-
nation if subjected to heat.  But one observer now made
another  experiment, which seemed to go entirely  the
other way, and puzzled him altogether.   He took some
of  this boiled infusion that I have been  speaking of,
and by the use of a  mercurial  bath—a  kind of trough
used  in  laboratories—he deftly inverted a vessel  con-
         4 
74         ORIGINATION OF LIVING BEINGS.
taining the infusion into the mercury, so that the latter
reached a little beyond  the level of the mouth of the
inverted vessel.  You see that he thus  had a quantity
of the infusion shut off  from  any possible communica-
tion with the outer air by being inverted upon a bed of
mercury.
    He then prepared  some pure oxygen and nitrogen
gases, and passed them by means of a tube going from
the outside of the vessel, up through the mercury into
the infusion; so that he thus had it exposed to a per-
fectly pure atmosphere of the same  constituents as the
external air.   Of course, he expected he would get no
infusorial  animalcules at all  in that infusion; but, to
his great dismay and discomfiture, he found he almost
always did get them.
    Furthermore  it  has  been found that  experiments
made in the manner described above answer well with
most  infusions;  but that  if you fill the  vessel with
boiled milk, and  then stop the neck with  cotton-wool,
you will  have infusoria.  So that you see there were
two experiments that brought you to one kind of con-
clusion, and three  to  another; which was a most  un-
satisfactory state of things  to arrive at in a  scientific
inquiry.
    Some few years after this,  the question  began to be
very hotly discussed in France. There was M. Pouchet,
a professor at Kouen, a very learned man, but certainly
not a very rigid experimentalist.  He published a num-
ber of experiments of his own, some of which were very
ingenious, to show that if you went to work in a proper
way, there was a truth in  the doctrine of  spontaneous
generation.  Well, it  was one of the  most fortunate
things in the world that  M. Pouchet took up this ques- 
            ORIGINATION OF LIVING BEINGS.          75

tion, because it induced a distinguished French chemist
M. Pasteur, to take up the question on  the other side;
and he has certainly worked it out in the most perfect
manner.   I am glad to say, too, that  he has published
his researches in time to  enable me to give you an ac-
count of them.  He verified all the experiments which
I have just mentioned to you—and then finding those
extraordinary anomalies, as in the case  of the mercury
bath and the milk, he set himself to work  to discover
their nature.  In the case of milk he found it to be a
question of temperature.   Milk  in  a fresh  state is
slightly alkaline; and it is a very curious circumstance,
but this very slight degree of alkalinity seems to have
the effect of preserving the  organisms  which fall into
it from the air from being destroyed  at a temperature
of 212°, which is the boiling point.  But if  you raise
the temperature 10° when you boil it, the milk behaves
like everything else ; and if the air with which it comes
in contact, after  being boiled  at  this  temperature, is
passed through a red-hot tube, you will not get a trace
of organisms.
    He then turned his  attention to the mercury bath,
and found on examination  that the surface of the mer-
cury was almost  alwa}<s  covered with a very fine dust.
He found  that even  the mercury itself was  positively
full  of  organic  matters;  that  from  being constantly
exposed to the air, it had collected an  immense num-
ber of these infusorial organisms from  the air.  Well,
under these circumstances he  felt that the  case was
quite clear, and that the  mercury was not what it had
appeared to M. Schwann to be—a  bar to the admission
of these organisms; but that, in reality, it acted as a
reservoir  from which the infusion  was  immediately 
76          ORIGINATION OF LIVING BEINGS.
supplied with the large quantity that had so puzzled
him.
   But not content  with  explaining the experiments
of others, M. Pasteur went to work  to satisfy himself
completely.   He said to himself:  " If my view is right,
and if, in point of fact, all these  appearances of spon-
taneous generation are  altogether  due to  the falling of
minute germs suspended  in  the  atmosphere,—why, I
ought  not only to be  able  to show the  germs, but I
ought to be able to  catch and sow them, and produce
the resulting organisms."  He, accordingly, constructed
a very ingenious apparatus to enable  him to accomplish
this trapping of this  " germ dust" in  the air.  He fixed
in the  window of his room a  glass tube, in the centre
of which he had placed  a  ball of gun-cotton, which,
as you all know, is  ordinary cotton-wool, which, from
having been  steeped in strong acid, is converted  into
a substance of great explosive power.  It is also solu-
ble in  alcohol and ether.   One end of the glass tube
was, of course, open to the  external air; and at the
other end of it he  placed an aspirator,  a contrivance
for causing a current of the external air to pass through
the tube.  He kept  his apparatus going for four-and-
twenty hours,  and then removed the dusted gun-cot-
ton, and dissolved it in alcohol and ether.  He then al-
lowed  this to stand for a few hours, and the result was,
that a very fine dust  was gradually deposited at the
bottom of it.  That dust, on being transferred to the
stage of a microscope, was found  to contain  an  enor-
mous  number  of starch grains.   You know that the
materials of  our food and the greater portion of plants
are composed of starch, and we are  constantly making
use of it in a variety of ways, so  that there is always 
ORIGINATION OF LIVING BEINGS.         77
a quantity of it suspended in the air.  It is these starch
grains which form  many of those bright specks that
we see dancing in a ray of light sometimes.  But be-
sides these, M.  Pasteur found also an immense number
of other organic substances  such as spores of fungi,
which had  been floating about in the air and had got
caged in this way.
   He  went farther, and said  to himself,  "If these
really are the things  that give rise to the appearance
of spontaneous generation, I  ought to be able to take
a ball of this dusted gun-cotton and put it into one of
my vessels, containing that  boiled infusion  which has
been  kept  away from the air, and  in  which no  in-
fusoria are at present developed, and then, if I am right,
the introduction  of this gun-cotton will give rise to
organisms."
   Accordingly, he  took one of these vessels of infu-
sion,  which had been kept eighteen nionths, without
the least appearance  of  life,  and by a most ingenious
contrivance, he managed to  break  it open  and intro-
duce  such  a ball of  gun-cotton, without allowing the
infusion or the cotton ball to come into contact with
any air but that which  had  been subjected to a red
heat,  and in twenty-four hours he had the satisfaction
of finding all the indications of what had been hitherto
called spontaneous generation.  He had succeeded in
catching the germs  and developing organisms in the
way he had anticipated.
   It now struck him that the truth of his conclusions
might be demonstrated  without  all the apparatus he
had  employed.   To do  this, he  took some decaying
animal or vegetable  substance, such  as urine, which is
an extremely decomposable substance, or the juice of 
 78         ORIGINATION OF LIVING BEINGS.

 yeast, or perhaps some other artificial preparation, and
 filled a vessel having a long tubular neck, with it.  He
 then boiled the liquid and bent that  long neck into an
 S  shape  or zig-zag, leaving  it open  at  the end.   The
 infusion then gave no trace of any appearance of spon-
 taneous generation, however long it might be left, as
 all the germs in the air were deposited in the beginning
 of the bent neck.   He then cut the tube close to the
 vessel, and allowed  the ordinary air to have free  and
 direct access; and the result of that was the appearance
 of organisms in it, as soon as the infusion had been
 allowed  to stand long enough to allow of  the  growth
 of those it received from the air, which was about forty-
 eight hours.  The result of M. Pasteur's experiments
 proved, therefore, in the most conclusive manner, that all
 the appearances of  spontaneous generation arose from
 nothing more than the deposition of the germs of or-
 ganisms which were constantly floating in the air.
   To  this conclusion, however,  the  objection was
 made, that if that were the cause, then the air would
 contain such an enormous number of these  germs, that
 it would  be a continual fog.   But M. Pasteur replied
 that they are not there in anything like the number we
 might suppose,  and that an exaggerated view has been
 held on that  subject; he showed that the chances of
 animal or vegetable life appearing in infusions, depend
 entirely on the conditions  under which they are  ex-
posed.  If they are exposed to  the ordinary atmosphere
 around us, why, of course,  you may have organisms
 appearing early.  But, on the other hand, if they are
 exposed to  air from a great height, or from some very
 quiet cellar, you will often not find  a single  trace of
life. 
ORIGINATION OF LIVING BEINGS.
79
   So that M. Pasteur arrived at last at the clear and
definite result, that all these appearances are like the
case of the worms in the piece of meat, which was re-
futed by Eedi, simply germs carried by the  air and
deposited in the liquids in which they afterwards ap-
pear.  For my  own part,  I  conceive  that, with the
particulars of M. Pasteur's experiments before us, we
cannot fail to arrive  at his  conclusions ;  and that the
doctrine of spontaneous generation has received a final
coup de grace.
    You, of course, understand that  all this in no way
interferes with the possibility of the fabrication of or-
ganic matters by the direct method to which  I  have
referred, remote as that possibility may be. 
LECTUEE  IV.
THE PERPETUATION OF LIVING BEINGS, HEREDITARY
          TRANSMISSION AND VARIATION.

   The inquiry which we undertook, at our last meet-
ing, into the  state of our knowledge of the causes of
the phenomena of organic nature,—of the past and of
the present,—resolved  itself into two  subsidiary  in-
quiries :  the  first was, whether we know anything,
either historically or experimentally, of the mode of
origin of living beings; the second subsidiary inquiry
was, whether, granting the origin, we know anything
about the perpetuation and modifications of the forms
of organic  beings.  The reply which I had to give to
the first question was altogether negative, and the chief
result of my last  lecture was, that, neither historically
nor experimentally, do we  at present know anything
whatsoever about the origin of living forms.   We saw
that, historically,  we are not likely to know anything
about it, although we may perhaps learn something ex-
perimentally ; but that at present we are an enormous
distance from the goal I indicated.
   I now,  then, take up the next question, What do
we know of the reproduction, the perpetuation, and the
modifications of the forms  of living beings, supposing 
         THE PERPETUATION OF  LIVING BEINGS.      81

that we have put the question as to their origination on
one  side, and have assumed  that at present the causes
of their origination are beyond us, and that we know
nothing  about them ?   Upon this question the state of
our knowledge is extremely different; it is exceedingly
large, and, if not complete, our experience is  certainly
most extensive.  It would be  impossible to lay it all
before you, and the most I can  do, or need do to-night,
is to take  up the principal points and put them before
you with such prominence as  may subserve the  pur-
poses of our present argument.
    The method of the  perpetuation of organic  beings
is of two kinds,—the asexual and the sexual.   In the
first the perpetuation  takes  place from and  by a  par-
ticular act  of an individual organism, wliich sometimes
may not be classed as belonging to any sex at all.  In
the  second case, it is in consequence of the mutual ac-
tion and interaction of certain portions of the organisms
of usually  two distinct  individuals,—the male and the
female.  The cases of asexual  perpetuation are by no
means so common as the cases  of sexual perpetuation ;
and they are by no means so common in the animal as
in the vegetable world.  You are all probably familiar
with the fact, as a matter of experience,  that you can
propagate  plants by means  of what are called " cut-
tings ;"  for example, that  by taking a cutting from a
geranium plant, and rearing it properly, by supply-
ing  it with light and warmth  and nourishment from
the earth, it grows up and takes the form of its parent,
having  all  the properties and  peculiarities of the ori-
ginal plant.
   Sometimes  this process,  which the gardener  per-
forms artificially, takes place  naturally; that  is to  say,
         4* 
 82      THE PERPETUATION OF LIVING BEINGS,

 a  little bulb, or portion of the plant, detaches itself,
 drops off, and becomes capable of growing as a separate
 thing.   That is the case with  many bulbous  plants,
 which throw off in this way  secondary bulbs, which
 are lodged in the ground and become developed into
 plants.  This is an asexual process, and from it results
 the repetition or reproduction of the form of the ori-
 ginal being from which the bulb proceeds.
   Among animals the same thing takes place.  Among
 the lower forms of animal life, the infusorial  animal-
 culse we have already spoken of throw off certain por-
 tions, or break  themselves up in various  directions,
 sometimes  transversely or  sometimes longitudinally ;
 or they may give off buds, wliich detach  themselves
 and  develop into  their  proper forms.  There  is the
 common fresh-water Polype, for instance, wliich multi-
 plies itself in this way.  Just in the same  way as the
 gardener is able to multiply and reproduce the pecu-
 liarities and characters of particular  plants by means
 of cuttings, so  can the physiological experimentalist,
 —as was  shown by the Abbe Trembley many  years
 ago,—so can he do the same thing with many  of the
 lower forms of  animal life.  M.  de Trembley  showed
 that you could  take a polype and cut it into two, or
 four, or many pieces,  mutilating  it  in  all  directions,
 and the pieces would still grow up and reproduce com-
 pletely the original form of the animal.   These are all
 cases of asexual  multiplication, and there are other in-
 stances, and still more extraordinary ones, in  which
this process takes place naturally, in  a more hidden, a
more  recondite kind of way.   You are all  of you fa-
miliar  with those little green insects, the Aphis or
blight, as it is called.   These little  animals,  during 
       HEREDITARY TRANSMISSION AND VARIATION.    83

 a very considerable part of their existence, multiply
 themselves by means of a kind of internal budding, the
 buds being developed  into essentially asexual animals,
 which are neither male  nor female ; they become con-
 verted into young Aphides, which repeat the process,
 and their offspring after them, and so  on again; you
 may go on for nine or  ten, or even twenty or more suc-
 cessions ;  and there is  no very good reason to say how
 soon it might terminate, or how long it might not go
 on if the proper conditions of warmth and nourishment
 were kept up.
    Sexual  reproduction is  quite  a distinct matter.
 Here,  in all these cases,  what is required is the detach-
 ment of two portions of  the parental organisms, wliich
 portions we know as the egg or the spermatozoon.  In
 plants it  is the ovule and  the pollen-grain, as  in the
 flowTering plants, or  the  ovule and the antherozooid, as
 in the fiowerless.  Among all forms of animal life, the
 spermatozoa proceed from the male sex, and the egg is
 the  product of the female.  Now, what is remarkable
 about  this mode of  reproduction is this, that the egg
 by itself, or the spermatozoa by themselves, are unable
 to assume the parental  form;  but if they be brought
 into contact with one another, the effect of the mixture
 of organic substances  proceeding from twro sources ap-
 pears to confer an altogether new vigour to the mix-
 ed product.  This process is brought about, as we all
 know,  by  the sexual intercourse of the two sexes, and
 is called the act of impregnation.  The result of this
 act on  the part of the  male and female is, that the
formation of a new being is set up in the ovule or egg;
this ovule or egg soon begins to be divided  and sub-
divided, and to be fashioned into various  complex or- 
 84      THE PERPETUATION  OF  LIVING BEINGS,

 ganisms, and eventually to develop into the form  of
 one of its parents, as I explained in the first lecture.
 These  are the processes  by which the perpetuation of
 organic beings is  secured.  Why there  should be the
 two  modes—why  this re-invigoration  should  be re-
 quired on the part of the  female element  we do not
 know; but  it is most assuredly the fact, and it is pre-
 sumable,  that,  however long  the  process  of asexual
 multiplication could  be continued,—I say there is good
 reason to believe that it would  come to an end if a new
 commencement were  not obtained by a conjunction of
 the two sexual elements.
   That  character which is common to these two dis-
 tinct  processes  is  this, that, whether we consider the
 reproduction, or perpetuation,  or modification  of or-
 ganic beings as they take place asexually,  or as they
 may take place sexually,—in either case, I say, the off-
 spring has  a constant tendency  to assume, speaking
 generally, the character of the parent.  As  I said just
 now, if you take a slip of a plant, and tend it with care,
 it  will eventually  grow  up and  develop into a plant
 like that from which it had  sprung; and this tendency
 is so strong that, as gardeners know, this  mode of mul-
 tiplying by  means of cuttings is the only secure mode
 of propagating very many varieties of plants  ; the pecu-
 liarity of the primitive stock seems to be better  pre-
 served if you propagate it  by means of  a slip than if
you resort to the sexual mode.
   Again, in experiments upon  the lower animals, such
 as the polype, to which I have referred, it is most ex-
traordinary  that, although cut  up into various pieces,
 each particular piece will grow  up into the form of the
primitive stock ; the head, if separated, will reproduce 
      HEREDITARY TRANSMISSION AND  VARIATION.    85

the body and the tail; and if you cut off the tail, you
will find that that will reproduce the body and all the
rest  of  the  members,  without  in  any way deviating
from  the plan of the. organism from wliich these por-
tions  have been detached.  And  so far does  this go,
that  some experimentalists  have carefully examined
the lower orders of animals,—among them the Abbe
Spallanzani, who made a number of experiments upon
snails and salamanders,—and  have found  that they
might mutilate them to an incredible extent; that you
might cut off the jaw or the  greater part of the head,
or the leg or the tail, and repeat  the experiment sev-
eral times, perhaps, cutting off the same member agairf
and again ;  and yet  each  of those types would  be
reproduced according to  the primitive type: nature
making no mistake, never putting on a fresh kind of
leg, or head, or tail, but always tending to repeat and
to return to the primitive type.
    It is the same in sexual  reproduction : it is a mat-
ter of perfectly common experience, that the tendency
on the part of the offspring always is, speaking broadly,
to  reproduce the form of the parents.  The proverb
has it that the thistle does not bring forth grapes ;  so,
among  ourselves, there is always a likeness,  more or
less marked and distinct, between children and their
parents.  That is a matter of familiar and ordinary ob-
servation.   We notice the same thing occurring in the
cases of the domestic  animals—dogs, for instance, and
their offspring.  In all these cases of propagation and
perpetuation, there seems to be a tendency in the off-
spring to take the characters of the parental organisms.
To that tendency a  special  name is given—and as I
may very often use it, I will write  it up here on this 
86      THE PERPETUATION OF LIVING BEINGS,

black-board that you  may remember it—it is  called
Atavism;  it expresses this tendency to revert  to the
ancestral type, and comes from the Latin word atavus,
ancestor.
   Well, this Atavism wliich I shall speak of, is, as I
said  before, one  of the most marked and striking ten-
dencies of organic beings; but, side by side with this
hereditary  tendency, there is  an equally distinct and
remarkable  tendency  to variation.   The tendency to
reproduce the original stock has, as it were, its  limits,
and  side by side with  it there is a tendency to vary in
certain directions, as if there were  two opposing pow-
ers working upon the  organic being, one tending to
take it in a straight line, and the other tending to make
it diverge from  that straight  line, first to one  side and
then to the other.
   So that you  see these two tendencies need not pre-
cisely contradict one  another,  as the ultimate  result
may not always  be very remote from what would have
been the case if the line had been quite straight.
   This tendency to variation  is less marked in that
mode of propagation which takes place asexually ; it is
in that mode that the minor characters of animal and
vegetable structures are  most completely  preserved.
Still, it  will happen  sometimes, that the gardener,
when he has planted a cutting of  some favourite plant,
will  find, contrary to  his expectation, that  the slip
grows up a  little different from the primitive stock—
that it produces flowers of a different colour or  make,
or some deviation in one way or another.  This is what
is called the " sporting " of plants.
   In  animals the phenomena of asexual propagation
are so obscure, that at present we cannot  be said to 
      HEREDITARY TRANSMISSION AND VARIATION.    87

know much about them ; but if we turn to that mode
of perpetuation which results from the sexual process,
then we find variation a perfectly constant occurrence,
to a certain extent;  and, indeed, I think that a certain
amount of variation from the primitive stock is the
necessary result of the method of sexual propagation
itself; for, inasmuch as the thing  propagated proceeds
from  two organisms of different sexes and different
makes arid  temperaments, and as the offspring is to be
either of one sex or the other, it is quite clear that it
cannot be an exact diagonal of the two, or it would be
of no sex  at all; it cannot be an exact intermediate
form  between that of each of  its  parents—it must de-
viate to one side or the other.  You do not find that
the male follows the precise type of the male parent,
nor does the female always inherit the precise charac-
teristics of the mother,—there is  always a proportion
of the female character in the male offspring, and of
the male character in the female offspring.  That must
be quite plain to all of you who have looked at all at-
tentively on your own children or those of your neigh-
bours ; you will have noticed how very often  it may
happen that the son shall exhibit the maternal  type of
character, or the daughter possess the characteristics
of the father's family.  There  are all sorts of intermix-
tures and intermediate conditions  between the two,
where  complexion,  or beauty, or fifty other different
peculiarities belonging to either side of the house, are
reproduced  in other members of the same family.  In-
deed, it is sometimes to be remarked in this  kind of
variation, that  the  variety belongs, strictly speaking,
to  neither of the immediate parents; you will see  a
child in a family who is not like  either its father or its 
88      THE  PERPETUATION OF LIVING BEINGS,

mother;  but some old person who knew its  grand-
father or grandmother, or, it may be, an uncle, or, per-
haps,  even a more distant  relative, will see a great
similarity  between the child and one of these.  In this
way it constantly happens  that the characteristic  of
some  previous member of the family comes out and
is reproduced and recognized in the most unexpected
manner.
   But  apart from that  matter of general experience,
there  are some cases which put that curious mixture in
a very clear light.  You are aware that the offspring of
the Ass and the Horse, or rather of the he-Ass and the
Mare, is what is called a Mule ; and, on the other hand,
the offspring of the Stallion and the she-Ass is what is
called a Jlinny.   It is a very rare thing in this country
to  see a Hinny.  I never  saw one myself;  but they
have been very  carefully studied.   Now, the curious
thing is this, that although you have the same elements
in the experiment in each case, the offspring is entirely
different in character,  according  as the male  influence
comes from the Ass or the Horse.  Where the Ass is
the male, as in the case of the Mule, you find that the
head is  like that of the Ass, that the ears are long, the
tail is tufted at the end, the  feet are small, and the
voice  is an unmistakable bray ; these  are all points
of  similarity  to the Ass; but, on  the other hand, the
barrel of the  body and the cut of  the  neck  are  much
more like  those of the Mare.   Then, if you look  at the
Hinny,—the  result of the union  of the Stallion and
the she-Ass, then you  find it is the Horse that has the
predominance ;  that the head  is more like that of the
Horse, the ears are shorter, the legs coarser,  and the
type is altogether  altered;  while the voice, instead 
      HEREDITARY TRANSMISSION AND VARIATION.     89

of being a bray, is the ordinary neigh of the Horse.
Here, you see, is a most curious thing:  you take ex-
actly the same elements, Ass and Horse, but you com-
bine the sexes in a different manner, and the result is
modified accordingly.  You have in this case, however,
a result which is not general and universal—there is
usually an important  preponderance,  but  not always
on the same side.
   Here, then, is one intelligible, and, perhaps,  neces-
sary cause of variation: the fact, that there  are two
sexes sharing in  the production of the offspring, and
that the share taken by each is different and variable,
not only for each combination, but also for different
members of the same family.
   Secondly, there is a variation, to a certain extent,—■
though in all probability the influence of this cause has
been very  much exaggerated—but there is no  doubt
that variation is produced, to a certain  extent, by what
are commonly known as external conditions,—such as
temperature, food, warmth, arid moisture.   In the long
run, every  variation depends, in some sense, upon ex^
ternal  conditions, seeing that everything has a cause
of its own.  I use the term " external conditions " now
in the sense  in which  it is ordinarily  employed: cer-
tain it  is, that external conditions have a definite effect.
You may take a plant which has single flowers, and
by dealing with the soil, and nourishment, and  so on,
you  may by-and-by convert single flowers into double
flowers, and make thorns  shoot  out into branches.
You may thicken or make  various modifications in the
shape of the  fruit.  In animals, too,  you may produce
analogous changes in this way, as in the case of that
deep bronze colour which persons rarely lose  after 
 SO       THE PERPETUATION OF LIVING BEINCiS,

 having passed any length of time in tropical countries.
 You may also alter the development of the  muscles
 very much, by dint of training;  all the world knows
 that exercise has a great effect in this way; we always
 expect to find the arm of a blacksmith hard and wiry,
 and possessing a large development of the  brachial
 muscles.   No doubt, training, which is one of the forms
 of  external  conditions,  converts  what  are originally
 only instructions, teachings,  into habits,  or, in other
 words, into  organizations, to  a great extent;  but this
 second cause of variation cannot be considered to  be
 by  any means a large  one.  The third cause that I
 have to mention, however, is  a very extensive  one.  It
 is one  that,  for want of  a better name, has been called
 " spontaneous variation ; " which means that when we
 do not know anything about the cause of phenomena,
 we  call it spontaneous.  In the orderly chain of causes
 and effects in this world, there are very few things of
 which  it can  be said with truth  that  they are spon-
 taneous.  Certainly not  in  these physical matters,—in
 these there is nothing of the kind,—everything depends
 on previous conditions.  But when we cannot trace the
 cause of phenomena, we call them spontaneous.
    Of  these variations, multitudinous as they  are, but
 little is known with perfect accuracy.  I will  mention
to you  some two or three cases, because they are very
remarkable  in  themselves, and also because I shall
want to  use them  afterwards.   Eeaumur,  a famous
French naturalist, a great many years ago, in the essay
which  he wrote upon the art of hatching chickens,—
which was indeed a very curious essay,—had occasion
to speak of variations and monstrosities.   One  very re-
markable case had come under his notice of a variation 
      HEREDITARY  TRANSMISSION AND  VARIATION.    91

in the form of a  human member, in the person of a
Maltese, of the name of Gratio Kelleia, who was born
with six fingers upon each hand, and the like number
of toes to each of his feet.  That was a case of  spon-
taneous variation.   Nobody knows  why he was born
with that number of fingers and toes, and as wre don't
know, we call it a case of " spontaneous" variation.
There is  another remarkable case also.  I select these,
because they happen  to have been observed and noted
very carefully at the time.  It frequently happens that
a variation occurs, but the persons who notice it do not
take any care in noting down the particulars, until at
length, when inquiries come to be made, the exact cir-
cumstances are forgotten ; and hence, multitudinous as
may be such " spontaneous"  variations,  it  is exceed-
ingly difficult to get at the origin of them.
   The second case is one of which you may find the
whole details in the " Philosophical  Transactions " for
the year 1813,  in a paper communicated by Colonel
Humphrey to the President  of the  Eoyal Society,—
" On a new Variety in the Breed of Sheep," giving an
account of a very remarkable  breed of sheep, which
at one time was well known in the  northern states of
America,  and which went by the name of the Ancon
or the Otter breed of sheep.   In  the year 1791, there
was  a farmer of the  name of Seth  Wright in Massa-
chusetts, who had  a flock of sheep, consisting of a ram
and, I think, of some twelve or thirteen ewes.  Of this
flock of ewes, one at the breeding-time bore a  lamb
which was very singularly formed; it had  a very long
body, very short legs, and those legs were bowed!  I
will  tell you by-and-by how this singular  variation in
the breed  of sheep came  to be noted, and  to have the 
 92      THE PERPETUATION OF LIVING BEINGS,

 prominence that it now has.  For the present, I  men-
 tion only these two cases;  but the extent of variation
 in the breed of animals is perfectly obvious to any one
 who has studied natural history with ordinary atten-
 tion,  or to any  person who  compares  animals  with
 others of the same kind.  It is strictly true that there
 arc never any two specimens wliich are exactly alike ;
 however similar, they will always  differ in some cer-
 tain particular.
    Now let us go back to Atavism,—to the hereditary
 tendency I  spoke of.   What will come of a variation
 when you  breed from it, when Atavism conies, if I
 may say so, to intersect variation ?  The  two cases  of
 which I have mentioned the history, give a most excel-
 lent illustration  of what occurs.   Gratio Kelleia, the
 Maltese, married when he was twenty-two years of age,
 and, as  I suppose there were no six-fingered ladies in
 Malta,  he  married an  ordinary  five-fingered person.
 The result  of that marriage  was  four children; the
 first,  who  was  christened Salvator,  had six  fingers
 and six toes, like his father; the second was  George,
 who had five fingers  and toes, but one  of them was
 deformed, showing a  tendency to variation; the third
 was Andre; he  had five fingers and five toes, quite
perfect; the fourth was a girl,  Marie;  she had five
fingers  and  five toes,  but her thumbs were deformed,
showing a tendency towards the sixth.
   These children grew  up, and when they  came  to
adult  years, they all  married, and of course  it  hap-
pened that they all married five-fingered and five-toed
persons.  Now let us  see what were the  results.  Sal-
vator  had four children; they were two boys, a  girl,
and another boy: the first two boys and  the girl were 
      HEREDITARY TRANSMISSION AND VARIATION.     93

six-fingered and  six-toed like their  grandfather;  the
fourth boy had only five fingers and five toes.  George
had  only four children: there were two  girls with si x
fingers and six toes; there was one girl with six fingers
and five toes on the right side, and five fingers and five
toes  on the left  side, so that she was half and half.
The  last, a  boy, had  five  fingers and  five toes.  The
third, Andre, you will recollect, was perfectly well-
formed, and he had  many children whose hands and
feet  were all  regularly developed.   Marie,  the last,
who, of course, married a man who had  only five  fin-
gers, had four children : the first, a boy, was born with
six toes, but the other three were normal.
   Now  observe  what very extraordinary phenomena
are presented  here.  You  have an accidental variation
arising from what you may call a monstrosity; you
have that monstrosity tendency or variation diluted in
the first  instance  by an admixture with a female  of
normal construction,  and you would naturally expect
that, in the results of such  an union, the monstrosity,
if repeated, would be in  equal proportion  with  the
normal  type; that is to say, that the children would
be half  and half, some taking  the peculiarity of  the
father, and the others being  of the purely normal type
of the mother; but you see we  have a  great prepon-
derance of the abnormal type.  Well, this comes to be
mixed once more with the  pure,  the normal type, and
the abnormal  is again produced  in  large  proportion,
notwithstanding the second dilution.  Now what would
have happened if these abnormal types had intermar-
ried with each other; that  is to say, suppose the two
boys of Salvator had taken it into their heads  to marry
their first cousins, the two first  girls of  George, their 
94      THE PERPETUATION OF LIVING BEINGS,

uncle?  You will remember that these are all of the
abnormal type of their grandfather.   The result would
probably have  been,  that their  offspring would  have
been in every case  a  further development  of that ab-
normal type.  You  see it is only in  the  fourth, in the
person of Marie, that the tendency, when it appears
but slightly in the second generation, is washed out
in the third, while the progeny of Andre, wdio escaped
in the first instance, escape altogether.
   We have in this case a  good example  of nature's
tendency to  the perpetuation of a variation.   Here  it
is certainly  a variation which carried  with it no use
or benefit; and yet you  see the tendency to perpetu-
ation  may be so strong, that, notwithstanding a great
admixture of pure blood, the variety  continues itself
up to the third generation, which is  largely marked
with  it.   In this case, as I have  said, there was no
means of the second generation intermarrying with any
but five-fingered persons, and  the question  naturally
suggests  itself, What would have been  the  result of
such  marriage?  Reaumur  narrates this case only  as
far  as the third generation.  Certainly it would have
been  an  exceedingly curious thing  if we  could have
traced this matter any further;  had the cousins inter-
married, a six-fingered variety of the human race might
have been set up.
   To show you that this supposition is by no means
an unreasonable one, let me now point out what took
place in the case of Seth Wright's sheep, where it hap-
pened to be a matter of moment to  him to obtain a
breed or raise a flock of  sheep like that accidental va-
riety  that I have described—and  I will tell  you why.
In that part of Massachusetts where Seth  Wright was 
       HEREDITARY TRANSMISSION AND VARIATION.    95

 living,  the  fields  were separated by fences,  and the
 sheep, which were very active and robust, would roam
 abroad, and without much difficulty jump over these
 fences into other people's farms. As a matter of course,
 this exuberant activity on the part of the sheep con-
 stantly gave rise to all sorts of quarrels, bickerings and
 contentions among the farmers of the neighbourhood;
 so it occurred to  Seth Wright, who was, like his suc-
 cessors, more or less 'cute, that if he could get a stock
 of sheep like those with the bandy legs, they would not
 be able to jump over the fences so readily, and he acted
 upon that idea.  He killed his  old ram, and as soon as
 the young one arrived at maturity, he  bred altogether
 from it.  The  result was even more striking than in the
 human experiment which  I mentioned just now.  Col-
 onel Humphreys testifies that it always happened that
 the offspring were either pure Ancons or pure ordinary
 sheep ;  that in no case was there any mixing of the
 Ancons with  the  others.  In  consequence of this, in
 the course of a very few years, the farmer was able to
 get a very considerable flock of this yariety, and a large
 number of them were spread throughout Massachusetts.
 Most unfortunately, however—I suppose it was because
 they were so common—nobody took enough notice of
 them to preserve their skeletons ; and although Colonel
 Humphreys states that he sent a skeleton to the presi-
 dent of the Royal Society at the same time  that he
forwarded his  paper, and I am afraid that  the variety
has entirely disappeared; for a short time after these
 sheep had become prevalent in that district, the Merino
sheep were  introduced; and  as their wool was much
more valuable, and as they were a quiet race of sheep,
and showed no tendency to trespass or jump over fences, 
96       THE PERPETUATION OF LIVING BEINGS,

the Otter breed of sheep, the wool of which was infe-
rior to that of the Merino, was gradually allowed to die
out.
   You  see that these facts illustrate perfectly  well
what may be done if you take care to breed from stocks
that are similar to  each other.   After having got  a
variation, if, by crossing a variation with the original
stock, you multiply that variation, and  then take care
to keep that variation distinct from  the original stock,
and make them breed together,—then you may  almost
certainly produce a  race whose tendency to continue
the variation is exceedingly strong.
   This is what is called  "selection;"  and it is by exactly
the same process as that by which Seth Wright bred his
Ancon sheep, that our breeds of cattle, dogs, and fowls,
are obtained.   There are  some possibilities of  excep-
tion, but still, speaking  broadly, I may  say that  this is
the way in which all our varied races of domestic ani-
mals have arisen; and you must understand that it is
not one peculiarity or one characteristic alone in which
animals may vary.   There is not a  single  peculiarity
or characteristic of any kind, bodily or mental, in which
offspring may not vary to a certain extent from the
parent and other animals.
   Among ourselves this is well known. The simplest
physical  peculiarity is  mostly reproduced.   I know a
ease  of a man whose wife has the lobe of one her ears
a little flattened. An ordinary observer might scarcely
notice  it, and yet every  one of her children has an
approximation  to  the   same  peculiarity to some ex-
tent.
  If you look  at the other extreme, too, the gravest
diseases,  such as gout, scrofula, and consumption, may 
      HEREDITARY TRANSMISSION AND VARIATION.     97

be handed down with just the same certainty and per-
sistence as we noticed in the perpetuation of the bandy
legs of the Ancon sheep.
    However, these facts are best illustrated in animals,
and the extent of the  variation, as is well known, is
very  remarkable in dogs.   For  example, there  are
some  dogs very much smaller than others ; indeed,  the
variation is so enormous that probably the smallest dog
would be about  the size of the head of the largest;
there are very great variations in the structural forms
not only of the skeleton  but also in the  shape of  the
skull, and in the proportions of the face and the  dis-
position of the teeth.
    The Pointer, the Retriever, Bulldog, and the Ter-
rier, differ very greatly, and  yet  there is  every reason
to believe that every one  of these races has arisen from
the same source,—that all  the most important  races
have  arisen by this  selective breeding from accidental
variation.
    A still more  striking  case of what may be done by
selective breeding, and  it  is a better case, because there
is no chance of that partial  infusion of error  to which
I  allude, has been studied very carefully by  Mr. Dar-
win,—the case of the  domestic  pigeons.  I  dare  say
there may be some among you who may be pigeon
fanciers, and I  wish  you  to understand  that in  ap-
proaching the subject, I would speak with all  humility
and hesitation, as I regret to say that I am not a pigeon
fancier.  I know it is  a great art  and  mystery, and a
thing upon which a  man  must not speak lightly ;  but
I shall endeavour, as far as  my understanding goes, to
give you a summary of the  published and unpublished
information which I  have  gained from Mr. Darwin.
         5 
98      THE PERPETUATION OF LIVING BEINGS,

   Among the enormous variety,—I believe there are
somewhere about a hundred and fifty kinds of pigeons,
—there are four kinds which may be selected as repre-
senting the extremest divergences of one kind from an-
other.  Their names are the Carrier, the Pouter, the
Fantail, and the Tumbler.  In these large diagrams
that  I have here they are each represented  in  their
relative sizes to each other.  This first one is  the Car-
rier ;  you  will  notice  this large excrescence on  its
beak;  it has a comparatively small head ;  there is a
bare space round the  eyes ; it has a long neck, a very
long beak, very strong legs, large feet, long wings, and
so on.  The second one is the Pouter, a very large bird,
with very long legs  and beak.   It is called the Pouter
because it is in the  habit of causing its gullet to swell
up by inflating it with air.  I should tell you that all
pigeons have a tendency to do this at times, but in the
Pouter it is carried to an enormous  extent.   The birds
appear to be quite proud  of their  power  of  swelling
and puffing themselves out in this way; and I think it
is about as droll a sight as you can well see to look  at
a cage full of these pigeons puffing and blowing them-
selves out in this ridiculous manner.
   This diagram  is a representation of the  third kind
I mentioned—the Fantail.   It is, you see, a small bird,
with exceedingly small legs and a very small beak.
It is most curiously  distinguished by the size and  ex-
tent  of its tail, which,  instead of containing fourteen
feathers, may have  many more,—say thirty, or even
more—I believe there are some with as many as forty-
two.  This bird  has a curious habit of spreading out
the feathers of its tail in  such a way that  they reach
forward, and touch its head ; and if this can be accom- 
       HEREDITARY TRANSMISSION AND VARIATION.    99

 plished, I believe it is looked upon as a point of great
 beauty.
    But here is the  last great variety,—the Tumbler •
 and of that great variety, one of the principal kinds,
 and one most prized, is the specimen represented here
 —the short-faced  Tumbler.  Its beak, you see, is  re-
 duced to a mere nothing.  Just compare the beak of
 this one and that of the first one, the Carrier—I believe
 the  orthodox  comparison of the  head and beak of a
 thoroughly well-bred Tumbler  is  to stick an oat into a
 cherry, and that will give you the proper relative pro-
 portions of the head and beak.  The feet and legs are
 exceedingly small, and  the bird appears to be quite a
 dwarf when placed side by side with this great Carrier.
    These  are differences enough in regard  to their ex-
 ternal appearance;  but these  differences  are  by  no
 means the whole or even the most important of the dif-
 ferences wliich obtain between  these birds.  There is
 hardly a single point of their structure which has not
 become more or less altered ; and  to give you  an idea
 of how extensive these alterations are, I have here some
 very good skeletons, for which I am indebted  to my
 friend Mr. Tegetmeier, a great  authority in these mat-
 ters ; by means of which, if you examine them by-and-
 by, you will be able to see the  enormous difference in
 their bony structures.
   I  had  the privilege, some  time ago, of access to
 some important MSS. of Mr. Darwin, who, I may tell
 you, has taken very  great pains and spent much valu-
 able time and  attention on the investigation of these
 variations, and getting  together all the facts that bear
 upon them.  I obtained from these MSS.  the  follow-
ing summary of the  differences  between the  domestic 
100      THE PERPETUATION OF LIVING BEINGS,

breeds of pigeons; that is to say, a notification of the
various points in which their organization differs.   In
the first place, the back of the skull may differ a good
deal, and the development of the bones of the face may
vary a great deal; the back varies a  good deal;  the
shape of the  lower jaw varies;  the tongue varies very
greatly, not only in correlation  to the  length and size
of the beak, but it seems also to have a kind of inde-
pendent  variation of its own.   Then  the amount  of
naked skin round the eyes, and at the base of the beak,
may vary enormously; so may  the length of the eye-
lids,  the shape of the  nostrils,  and the length of the
neck.  I have already noticed the habit of blowing out
the gullet,  so remarkable in the Pouter, and compara-
tively  so in the others.  There  are  great differences,
too, in the  size of the female and the  male, the shape
of the body, the number and width of the  processes of
the ribs, the development  of the  ribs, and  the size,
shape, and  development of the  breastbone.  We may
notice, too,—and I mention the fact because it  has
been disputed by what is  assumed to be high author-
ity,—the variation in number of the sacral vertebrae.
The  number  of  these varies from  eleven  to fourteen,
and that without any diminution in the number of the
vertebrae of the back or of the tail.   Then the number
and position of the tail-feathers may vary enormously,
and so may the number of the primary and secondary
feathers of the wings.  Again,  the length of the feet
and of the beak,—although they have no relation to
each other, yet  appear to  go together,—that is, you
have a long beak wherever you  have long feet.  There
are differences also in the periods of the acquirement of
the perfect  plumage,—the size and shape of the eggs,— 
       HEREDITARY TRANSMISSION AND VARIATION.    101

the nature of flight, and the powers of flight,—so-call-
ed "homing" birds having enormous flying powers ;*
while, on the other hand, the little Tumbler is so called
because  of its extraordinary faculty of turning head
over  heels  in the air, instead of pursuing a distinct
course.  And, lastly, the dispositions and voices of the
birds may vary.   Thus the case of the pigeons shows
you that there is  hardly a single particular,—whether
of instinct, or habit,  or bony structure, or of plumage,
■—of either the internal economy or the external shape,
in which some variation or change may not take place,
which, by selective breeding, may become perpetuated,
and  form the  foundation  of, and give rise to, a new
race.
   If you  carry in your mind's eye these four varieties
of pigeons, you will bear with you as good a notion as
you can have, perhaps, of the enormous extent to which
a deviation from  a primitive  type may be carried by
means of this process of selective breeding.

   * The " Carrier,'''' I learn from Mr. Tegetmeier, does not carry ;
a high-bred bird of this breed being but a poor flier.  The birds
which fly long distances,  and  come home,—" homing " birds,—
and are consequently used  as carriers, are not " carriers " in the
fancy sense. 
LECTURE  Y.
THE CONDITIONS  OF EXISTENCE AS AFFECTING  THE
        PERPETtJATION OF  LIVING BEINGS.

    In the last Lecture I endeavoured to prove to you
that, while, as a general rule, organic beings tend to
reproduce their kind, there is  in them, also, a constantly
recurring tendency to vary—to vary to a greater or to
a less extent.  Such  a variety, I pointed out to you,
might arise from causes wliich we do not understand ;
we  therefore called it spontaneous;  and it might come
into existence as a definite  and marked  thing, without
any gradations  between itself and the form which pre-
ceded it.   I further pointed  out, that such  a variety
having once arisen, might be perpetuated to some ex-
tent, and indeed to  a very marked extent, without any
direct interference, or without any exercise of that pro-
cess which  we called selection.   And then I  stated
further,  that by such selection, when exercised artifi-
cially—if you took care to breed only from those forms
which presented the same  peculiarities of any variety
which had  arisen in this manner—the variation  might
be perpetuated, as  far as we can see, indefinitely.
   The  next question, and it is an important one for
us, is  this:  Is there any limit to  the amount of varia- 
           PERPETUATION  OF LIVING BEINGS.        103

tion from the primitive stock which can  be produced
by this process of selective breeding ?  In considering
this  question, it will  be useful to class  the  character-
istics, in respect  of which organic beings vary,  under
two heads:  we may consider structural characteristics,
and we may consider physiological characteristics.
   In the first plage, as regards  structural characteris-
tics, I endeavoured to show you, by the skeletons which
I had upon  the table, and by reference to a great many
well-ascertained  facts,  that the  different  breeds  of
Pigeons, the  Carriers,  Pouters,  and Tumblers,  might
vary in any of their internal and important structural
characters to a very great degree ; not only might there
be changes in the proportions of the skull, and the char-
acters of the feet and beaks, and so on;  but  that there
might  be an absolute difference  in the number of the
vertebrae of the back, as in the sacral vertebrae of the
Pouter; and  so great is the extent  of the variation in
these and similar characters that I pointed out to you,
by reference to  the  skeletons and the  diagrams, that
these extreme varieties may absolutely differ  more from
one another in their structural characters than do what
naturalists call distinct Species of pigeons;  that is to
say, that they differ so much in structure that there is
a greater difference between the Pouter and the Tum-
bler than there is between such wild and distinct forms
as the Rock Pigeon  or the Ring Pigeon,  or the Ring
Pigeon and the Stock Dove; and indeed the differences
are of greater value than this, for the structural  differ-
ences between these domesticated pigeons are such as
would  be admitted by a naturalist, supposing he knew
nothing  at  all about their origin, to  entitle them to
constitute even distinct  genera. 
 104          CONDITIONS AFFECTING THE

    As I have used this term Species,  and shall  proba-
 bly use it a good deal, I had better perhaps  devote a
 word or two to explaining what I mean by it.
    Animals and  plants are divided into groups, which
 become  gradually smaller, beginning with  a Kingdom,
 which is divided into  Sub-Kingdoms ; then come the
 smaller divisions called Provinces ; and so on from  a
 Province to  a Class, from  a Class to  an Order, from
 Orders  to Families, and from these to Genera, until
 we come at length to the  smallest groups of animals
 which can be defined  one from the other  by  constant
 characters, which are  not  sexual; and these are what
 naturalists call Species in practice, whatever they may
 do in theory.
    If in a state of  nature you find any two groups of
 living beings, which are separated one from the other
 by  some constantly-recurring  characteristic,  I don't
 care how slight and trivial,  so long as  it is defined and
 constant, and  does not  depend on sexual peculiarities,
 then all naturalists agree in calling them two species;
 that is what is meant by the use of the word species—
 that is to- say, it is,  for the practical naturalist, a mere
 question of structural differences.*
    We have seen now—to repeat this point once more,
 and it is very essential that we should rightly under-
 stand it—we have  seen that breeds,  known  to have
been derived from  a common  stock by selection, may
be as different in their structure from the original stock
 as species may be distinct from each other.
    But  is  the like true of the physiological charac-

  * I lay stress here on the practical signification of " Species." Wheth-
er a physiological test  between species exist or not, it is  hardly ever ap-
plicable by the practical naturalist. 
            PERPETUATION OF LIVING BEINGS.       105

 teristics of animals ?   Do the physiological differences
 of varieties amount in degree to those observed between
 forms which naturalists call distinct  species ?  This is
 a most important point for us to consider.
    As regards the great majority of physiological char-
 acteristics, there is no doubt that  they are capable of
 being developed, increased, and modified by selection.
    There is no doubt that breeds may be made as dif-
 ferent as species in many physiological  characters.  I
 have already pointed out to you very briefly the differ-
 ent habits of the breeds of Pigeons, all of which depend
 upon their physiological peculiarities,—as the peculiar
 habit  of  tumbling,  in the Tumbler,—the peculiari-
 ties  of flight,  in the  "homing"  birds,—the  strange
 habit of spreading out the tail, and walking in a pecu-
 liar  fashion, in  the Fantail,—and, lastly, the  habit of
 blowing out the gullet, so characteristic of  the Pouter.
 These are  all due to physiological modification, and in
 all these respects these birds differ as much from each
 other as any two ordinary species do.
    So with Dogs in their habits and  instincts.  It is
 a physiological peculiarity which leads the Greyhound
 to chase its prey by sight,—that enables  the Beagle to
 track it  by the  scent,—that impels the  Terrier to its
 rat-hunting propensity,—and that  leads  the Retriever
 to its  habit of retrieving.  These  habits and  instincts
 are all the results of physiological differences and pecu-
liarities, which have been developed  from a common
 stock,  at least there is every reason to believe so.  But
it is  a  most singular circumstance, that while you may
run  through almost the whole series  of  physiological
processes, without finding a check to your  argument,
you come at last to a point where you do find  a check,
       5* 
106
CONDITIONS AFFECTING THE
and that  is in the reproductive processes.  For there
is a most  singular circumstance in respect to natural
species—at least about some of them—and it would be
sufficient for the purposes of this argument, if it were
true of only one of them, but there is, in  fact, a great
number of such cases—and that is, that similar as they
may appear to be to mere races or breeds, they present
a marked peculiarity  in the reproductive  process.  If
you breed from the male  and female of the same race,
you of course have offspring of the like  kind, and if
you make the  offspring breed  together, you obtain the
same result, and  if you  breed from these again, you
will still  have the same kind of offspring; there is no
check.  But if you take members  of two  distinct spe-
cies, however similar  they may be to each other, and
make them breed together, you will find a check, with
some modifications and  exceptions, however, which I
shall speak of presently.   If you cross two such species
with each other, then,—although you may get offspring
in the case of the first  cross, yet, if you attempt to breed
from the products of that  crossing, which  are what are
called Hybrids—that is, if you couple a male  and a
female hybrid—then  the  result is that  in ninety-nine
cases out of a hundred you will get no offspring at all:
there will be no result whatsoever.
    The reason of this  is quite obvious in  some cases ;
the male hybrids, although possessing all  the external
appearances and characteristics of perfect  animals, are
physiologically imperfect and deficient in the structural
parts of the reproductive elements necessary to gener-
ation.  It is  said  to  be  invariably the  case with the
male mule, the cross between  the  Ass and the Mare;
and hence it is, that, although crossing the Horse with 
            PERPETUATION OF LrVING BEINGS.        107

 the Ass is easy enough, and is  constantly done, as far
 as I  am  aware, if you take two mules, a male and  a
 female, and endeavour to  breed from  them, you get
 no offspring whatever; no  generation will take place.
 This  is what  is  called  the sterility of the hybrids be-
 tween two distinct species.
    You see that this  is a  very extraordinary circum-
 stance ; one does not see why it should be.  The  com-
 mon teleological explanation is, that it is  to prevent the
 impurity  of the  blood  resalting from the crossing of
 one species with  another, but  you see  it does not in
 reality do anything of  the  kind.  There is nothing in
 this fact that hybrids cannot breed with  each other, to
 establish  such a theory; there  is  nothing to prevent
 the Horse breeding with the Ass, or  the  Ass with the
 Horse.  So that this  explanation  breaks down,  as  a
 great many explanations of  this kind do, that are  only
 founded on mere assumptions.
    Thus  you  see that there is  a  great difference be-
 tween " mongrels," which are crosses between distinct
 races, and " hybrids," which are crosses  between  dis-
 tinct  species.   The  mongrels are, so  far as we know,
 fertile with  one another. But between species, in many
 cases, you cannot succeed in obtaining  even the  first
 cross:  at  any  rate it is quite certain  that the hybrids
 are often absolutely infertile one with another.
    Here is a feature, then, great or small as it may be,
 which  distinguishes  natural species of animals.   Can
 we find any approximation to this in the  different races
 known  to be  produced by  selective  breeding from a
 common stock?  Up to the present  time the answer
to that question is absolutely a negative  one.  As far
as we know at present, there is  nothing approximating 
 108          CONDITIONS AFFECTING THE

 to this check.  In crossing the breeds between the Fan-
 tail and  the Pouter, the Carrier and  the  Tumbler, or
 any other variety or race you may name—so far as we
 know at present—there is no difficulty in breeding to-
 gether the mongrels.  Take the Carrier and the Fantail,
 for instance, and let them represent the Horse and the
 Ass in the case of distinct species; then  you have, as
 the result of their breeding, the Carrier-Fantail mon-
 grel,—we will say the male and female mongrel,—and,
 as far as we know, these two wdien crossed would not
 be less fertile  than the  original  cross, or than Carrier
 with  Carrier.  Here, you see, is a  physiological con-
 trast between the races produced by selective modifica-
 tion and natural species.  I shall inquire into the value
 of this fact, and of some modifying circumstances, by
 and by ;  for the present I merely put it broadly before
 you.
    But while  considering this question of the limita-
 tions  of  species, a word must be said about what  is
 called Recurrence—the tendency of races  which have
 been developed by selective breeding from varieties to
 return to their primitive type.   This is supposed  by
 many to  put an absolute limit to the extent of selective
 and all  other variations.   People say, " It is all very
 well to talk about producing these  different races, but
 you know very well that if you turned all these birds
 wild, these Pouters, and Carriers, and so on, they would
 all return to their primitive  stock."  This is very com-
 monly assumed to be a fact, and it is an argument that
is commonly brought forward  as  conclusive; but  if
you will take the trouble to inquire into it rather closely,
I think you will  find that  it is  not worth very much.
The first  question of course  is, Do they thus return to 
PERPETUATION OF LIVING BEINGS.        109
 the primitive stock ?  And  commonly as the  thing is
 assumed  and accepted, it is extremely difficult to get
 anything like good evidence of it. It is constantly said,
 for  example, that  if domesticated Horses  are turned
 wild, as they have been  in some parts of Asia Minor
 and South America, that they return at once to the
 primitive stock  from which they were bred.  But the
 first answer that you make to this assumption is, to
 ask who knows  what the  primitive stock  was;  and the
 second answer is, that in  that case the wild Horses of
 Asia Minor ought to be  exactly like  the wild Horses
 of  South America.  If they are  both like the same
 thing, they  ought manifestly  to  be like each other!
 The best  authorities, however,  tell you that it is quite
 different.   The wild  Horse of  Asia is said to  be of a
 dun colour,  with  a largish  head,  and a great many
 other peculiarities ; while the  best  authorities on the
 wild Horses of  South America tell you  that  there is
 nothing of this  sort in the wild Horses there;  the cut
 of their heads is very different,  and they are commonly
 chestnut or bay-coloured. It  is quite clear, therefore,
 that as by these facts there  ought to have been two
 primitive stocks, they go for nothing in support of the
 assumption that races recur to one primitive stock, and
 so  far as  this evidence  is concerned, it falls to  the
 ground.
    Suppose for  a  moment that  it were  so, and  that
 domesticated races, when turned wild, did return to
 some common condition,  I cannot see  that this would
prove much more than that similar conditions are likely
to produce  similar results; and  that  when you take
back domesticated  animals into what  we call  natural
conditions, you do  exactly the  same thing as  if you 
110
CONDITIONS AFFECTING THE
 carefully undid  all the work you had  gone through,
 for the  purpose of bringing  the  animal from its wild
 to its domesticated state.  I do not see anything very
 wonderful in the fact, if  it took all  that trouble to get
 it from a wild  state, that it should go back into its
 original state as soon as  you remove  the conditions
 which produced the variation to the domesticated form.
 There is an important fact, however, forcibly brought
 forward by Mr. Darwin, which  has been noticed in
 connection with the breeding of domesticated pigeons ;
 and it is, that however different these breeds of pigeons
 may be from each other, and we  have already noticed
 the great differences in these breeds, that if,  among
 any of those variations, you  chance to have a  blue
 pigeon turn up, it will be sure to have  the black bars
 across the wings, which are characteristic of the origi-
 nal wild stock, the Rock Pigeon.
    Now, this is certainly a very remarkable circum-
 stance ;  but I  do not  see  myself how it  tells  very
 strongly either one way or the other.  I think, in fact,
 that this argument in favour of recurrence to the primi-
 tive type might prove a great deal too  much for those
 who so constantly bring it forward.   For example, Mr.
 Darwin has very forcibly urged,  that nothing is com-
 moner than if you examine a dun horse—and I had an
 opportunity of  verifying this illustration lately, while
 in the islands of the West  Highlands, where  there are
 a great many dun  horses—to find  that horse exhibit
 a long black stripe down his back, very often  stripes
 on his shoulder, and very often stripes on his legs.  I,
myself, saw a pony of this description a  short time ago,
in a baker's cart, near Rothesay, in  Bute: it had the
long stripe down the back, and stripes on the shoulders 
           PERPETUATION OF LIVING BEINGS.       Ill

and legs, just like  those of the Ass, the Quagga, and
the Zebra.   Now, if we interpret the theory of recur-
rence as applied to this case, might it not  be said that
here was a case of a variation exhibiting the characters
and conditions of an animal occupying something like
an intermediate position between the  Horse, the  Ass,
the Quagga, and the Zebra, and from which these had
been  developed ?   In  the same way with  regard even
to  Man.  Every anatomist will tell  you that there is
nothing commoner, in  dissecting the human body, than
to meet with what are  called muscular variations—that
is,  if you  dissect  two bodies very carefully, you will
probably find that  the modes of attachment and inser-
tion of the muscles are not exactly the same in both,
there being  great  peculiarities in the mode in which
the muscles are arranged; and  it is very singular, that
in some dissections of  the human  body you will come
upon arrangements of  the muscles very similar indeed
to  the same parts  in the Apes.  Is the conclusion in
that case to be, that this is like the black  bars in the
case of the  Pigeon, and that it indicates a recurrence
to the primitive type from which the animals have been
probably developed?  Truly,  I think that the oppo-
nents  of modification  and variation had  better leave
the argument of recurrence alone, or it may prove alto-
gether too strong for them.
   To sum up,—the evidence as far  as we have gone
is against the argument as to any limit to divergences,
so far as  structure is  concerned; and in  favour of a
physiological  limitation.   By  selective  breeding  we
can produce structural divergences as  great as those
of species, but we cannot produce equal physiological
divergences.   For  the present  I  leave  the question
there. 
112
CONDITIONS AFFECTING THE
   Now, the next problem that lies before us—and it
is an extremely important one—is this: Does this selec-
tive breeding occur in nature ?  Because, if there is no
proof of it, all that I have been  telling  you goes for
nothing in accounting  for the origin  of species.   Are
natural causes competent to play the part of selection
in perpetuating varieties?  Here we labour under very
great difficulties.  In the last  lecture I had occasion
to point out to you  the  extreme difficulty of  obtaining
evidence even of the first origin of those varieties which
we  know to  have occurred in domesticated animals.
I told you, that almost always the  origin of these varie-
ties is overlooked,  so  that I could only produce  two
or three cases, as that  of Gratio  Kelleia and of the
Ancon sheep.   People  forget, or do not take notice of
them until they come to  have a  prominence;  and if
that is true of artificial cases, under our own  eyes, and
in animals in our own  care,  how  much more difficult
it must be to have at first hand good evidence of the
origin of varieties in nature!   Indeed, I do not know
that it is possible by direct evidence to prove the origin
of a variety in nature, or  to prove selective breeding ;
but I will tell you what we can prove—and this comes
to the same thing—that varieties exist in nature within
the limits of species, and, what  is more,  that when a
variety has come into  existence  in  nature,  there are
natural causes and conditions, which are amply com-
petent to play the part of a selective breeder ; and al-
though  that is not quite  the evidence that one would
like to have—though it is not direct testimony—yet it
is exceeding good and  exceedingly powerful evidence
in its way.
   As  to the first point, of  varieties existing  among 
•
            PERPETUATION OF LIVING BEINGS.        113

 natural species, I might appeal to the  universal experi-
 ence of every naturalist, and of any person who has
 ever turned any attention at all to the characteristics
 of plants and animals in a state of nature;  but I may
 as well take a few definite cases,  and I will begin with
 Man himself.
    I am one of those who believe that, at present, there
 is no evidence whatever for saying, that mankind sprang
 originally from any more than a single pair;  I must say,
 that I cannot see any good ground whatever, or  even
 any tenable sort of evidence, for believing that there
 is more than one species of Man.   Nevertheless, as you
 know, just as there are numbers of varieties in animals,
 so there are remarkable varieties  of men.  I speak not
 merely of those broad and distinct variations wliich
 you see at a glance.   Everybody, of course, knows the
 difference between a Negro and a white man, and can tell
 a Chinaman from an Englishman.  They each have pecu-
 liar characteristics of colour and physiognomy ;  but you
 must recollect that the characters of these races go very
 far deeper—they extend to  the bony structure, and to
 the characters of that most important of all organs to
 us—the brain ; so that, among men belonging to differ-
 ent races, or even within the same race, one man shall
 have a brain a third, or half, or even seventy per cent.
 bigger than another ;  and if you  take the whole range
 of human  brains, you will find a variation in some cases
 of a hundred per cent.   Apart  from these variations
 in the size of the brain, the characters of the skull vary.
 Thus if I  draw the figures of a Mongul  and a  Negro
 head on the blackboard, in  the  case of the  last the
breadth would be about  seven-tenths, and in the other
it  would  be  nine-tenths of  the  total  length.   So 
«v
114          CONDITIONS AFFECTING THE

that you see there is  abundant evidence of variation
among  men  in  their natural  condition.  And if you
turn to  other animals there is just the same thing.  The
fox, for example, which  has a very large  geographical
distribution all over Europe, and parts of  Asia, and on
the American Continent,  varies greatly.   There are
mostly large  foxes in  the North, and smaller ones in
the South.   In  Germany  alone, the foresters reckon
some eight different sorts.
    Of the tiger, no one supposes that there is more than
one species;  they extend from the  hottest parts of
Bengal, into  the dry, cold, bitter  steppes of Siberia,
into a latitude of 50°,—so that  they may even prey
upon the reindeer.  These tigers  have exceedingly dif-
ferent characteristics, but still they all keep their gen-
eral features, so that there is no doubt as to their being
tigers.  The  Siberian  tiger has a  thick  fur, a small
mane, and a  longitudinal stripe down the  back, while
the tigers of Java  and Sumatra differ in many impor-
tant respects from the tigers of Northern Asia.   So
lions vary; so birds vary; and  so, if you go  further
back and lower down in creation, you find fishes vary.
In  different  streams, in  the same  country even,  you
will find the  trout to be quite different to each other
and easily recognizable by those who fish  in the  par-
ticular  streams.   There  is  the same differences in
leeches; leech collectors can  easily point  out  to  you
the differences and the peculiarities which you your-
self would probably pass by ; so with fresh-water mus-
sels ; so, in fact, with every animal you can mention.
   In plants there is the same  kind of variation.  Take
such a case even as the common  bramble.  The bota-
nists are all at war about it; some of them wanting to 
            PERPETUATION OF LIVING BEINGS.        115

 make out that there are many species of it, and others
 maintaining that they are but many varieties of one
 species; and they cannot  settle to this day  which is a
 species and which is a variety !
    So that there can be no doubt whatsoever that any
 plant and  any animal may vary in nature;  that varie-
 ties may arise in the way I have described,—as sponta-
 neous varieties,—and that  those varieties may be per-
 petuated in  the  same  way  that  I  have shown  you
 spontaneous varieties are perpetuated ;  I  say, therefore,
 that there  can be no doubt as to  the  origin and  per-
 petuation of varieties in nature.
    But the question now is:—Does selection take place
 in nature ? is there anything like the operation of man
 in exercising selective breeding, taking place in nature ?
 You will observe that, at present, I say nothing about
 species; I wish to confine myself to  the  consideration
 of  the production of those natural races which every-
 body admits to exist.  The question is, whether in na-
 ture there  are  causes  competent to produce races, just
 in  the  same way  as  man is able to produce, by selec-
 tion, such races of animals as we have already noticed.
    When a variety has arisen,  the Conditions of Exist-
 ence are  such as to exercise an influence wliich is
 exactly comparable to that of artificial selection.  By
 Conditions of Existence I mean two things,—there are
 conditions which are furnished by the physical,  the in-
 organic world, and  there  are conditions of existence
 which are  furnished  by the organic world.  There is,
 in the first place,  Cllmate;  under  that head I in-
 clude  only temperature  and  the  varied amount of
moisture of  particular  places.  In  the  next  place
there is what is  technically  called  Station,  which 
116
conditions  affecting the
 means—given the  climate,  the particular  kind  of
 place in wliich an animal or a plant lives or grows ;  for
 example, the station of a fish is in the water, of a fresh
 water fish in fresh  water; the station of a marine fish
 is in the sea, and a marine  animal may have a station
 higher  or deeper.   So again with  land animals: the
 differences in their  stations are  those of different soils
 and neighbourhoods; some being best  adapted  to  a
 calcareous,  and others  to  an  arenaceous soil.  The
 third condition of existence is  Food, by which I mean
 food in the broadest  sence,  the supply of the  materials
 necessary to the existence of an  organic being; in the
 case of a plant the inorganic matters, such as carbonic
 acid, water, ammonia, and  the earthy salts or salines;
 in  the  case of the  animal the inorganic and organic
 matters, which we have seen  they require ; then these
 are  all, at least the  two first, what we may  call the
 inorganic or physical conditions of existence.   Food
 takes a  mid-place, and  then  come  the  organic condi-
 tions ; by which I mean the  conditions which depend
 upon the state of the rest of the organic  creation,  upon
 the  number and  kind of living  beings,  with which  an
 animal is surrounded.   You may class these under two
 heads:  there  are  organic  beings,  which  operate  as
 opponents, and there are organic beings wliich operate
 as helpers to any given organic  creature.  The  oppo-
 nents may be of two kinds : there are the indirect op-
ponents, which are what we  may call rivals ; and there
 are the  direct opponents, those which strive to destroy
 the creature;  and these we  call  enemies.  By  rivals I
 mean,  of course, in  the case of plants, those wliich
 require  for their support the  same kind of soil and
 station,  and, among  animals, those which require the 
           PERPETUATION  OF LIVING BEINGS.       117

same kind of station, or food, or climate ; those are the
indirect opponents ; the direct opponents are, of course,
those wliich  prey upon an  animal or vegetable.   The
helpers may also be regarded as direct and  indirect:  in
the case of a carnivorous animal, for example, a particu-
lar herbaceous plant may  in multiplying be an indirect
helper, by enabling the herbivora on which  the carni-
vore  preys to get more food, and thus to nourish the
carnivore more  abundantly; the direct helper may be
best illustrated by reference to  some  parasitic creature,
such as the tape-worm.  The tape-worm exists in the
human intestines, so  that the  fewer  there are of  men
the  fewer there  will be of tape-worms, other  things
being  alike.   It  is a  humiliating reflection,  perhaps,
that we may be classed as  direct helpers to the tape-
worm, but the fact is  so : we can all see that if there
were no men there would be no tape-worms.
   It is extremely difficult to estimate, in a  proper way,
the importance  and the working of the Conditions of
Existence.  I do  not think there were any of us who
had  the  remotest notion  of properly estimating them
until the  publication  of Mr.  Darwin's work, which has
placed them before us with  remarkable clearness ; and
I must endeavour, as  far as I can in my own fashion,  to
give you some notion  of how they work.  We shall find
it easiest to take a simple case, and one as free as possi-
ble from every kind of complication.
   I will  suppose, therefore, that all the habitable part of
this globe—the dryland, amounting to about 51,000,000
square miles,—I will suppose that the whole of that dry
land has the same climate, and that it is composed of
the same kind of rock or soil, so that  there will be the 
118
CONDITIONS  AFFECTING THE
 same station everywhere ; we thus get rid of the pecu-
 liar influence of different climates and stations.   I will
 then imagine that there shall be but  one organic being
 in the world, and  that  shall be  a  plant.  In  this we
 start fair.   Its  food  is to be carbonic acid, water and
 ammonia,  and the saline matters in the  soil, which are
 by the supposition, everywhere alike.  We  take one
 single plant,  with no opponents, no helpers,  and no
 rivals; it is to be a " fair field  and no favour."   Now
 I will ask  you to imagine further that it shall be a plant
 which shall produce every year fifty seeds, which is a
 very moderate  number  for a plant to produce; and
 that, by the  action of the winds and currents, these
 seeds shall be equally and gradually distributed over the
 whole surface of the land.   I want you now to trace
 out what will occur, and you will observe that I am not
 talking fallaciously  any  more  than  a mathematician
 does when he expounds his problem.  If you show that
 the conditions of your problem are such as may actually
 occur in nature, and do not transgress any of the known
 laws of nature  in working out  your proposition, then
 you are as  safe in the conclusion you arrive at, as is the
 mathematician in arriving at the  solution of his problem.
 In science,  the only way of getting rid of the complica-
 tions with which a subject of this kind is environed, is
 to work in this  deductive method.  What will be the
 result then ?  I  will suppose that every plant requires
 one square  foot of ground to  live upon ;  and the result
 will be that, in the course of  nine years, the plant will
 have occupied every single available spot in the whole
globe !  I have chalked upon the blackboard the figures
by which I arrive at the result:— 
PERPETUATION OF LIVING BEINGS.        119
Plant8-                                 Plants.
  1 x 50  in  1st  year  =                 50
50 x  50  " 2nd
2,500
            2,500 x  50  » 3rd   "   =             125,000
          125,000 x  50  " 4th   "   =           6,250,000
        6,250,000 x  50  " 5th   »   =         312,500,000
      312,500,000 x  50  « 6th   »   =       15,625,000,000
    15,625,000,000 x  50  " 7th   "   =      781,250,000,000
   781,250,000,000 x  50  » 8th   «   =    39,062,500,000,000
 39,062,500,000,000 x  50  " 9th   «   = 1,953,125,000,000,000
 51,000,000 sq. miles—the dry sur- j
  face of the earth x 27,878,400— [ =sq. ft. 1,421,798,400,000,000
  the number of sq. ft. in 1 sq. mile )___________________
                                 being  531,326,600,000,000
 square feet less than would be required at the end of the ninth year.
    You will  see  from  this that, at the end of the first
 year the single plant will have produced fifty more of its
 kind; by the end of the second  year these will have
 increased to 2,500 ; and so on, in succeeding years, you
 get beyond even trillions ;  and I am not at all sure that
 I could tell you what the proper arithmetical denomina-
 tion of the total number really is ; but, at any rate, you
 will  understand  the meaning of  all  those  noughts.
 Then you  see  that, at the bottom, I have taken the
 51,000,000 of square miles, constituting the surface of
 the dry land; and  as  the number of square  feet are
 placed  under  and abstracted from the number of seeds
 that would be produced in the ninth year, you can see
 at once that there would be an immense number more
 of plants  than there would be square feet of ground for
their  accommodation.   This is certainly quite enough
to prove my point; that between the  eighth and ninth
year after being planted, the  single plant would have
stocked the whole available surface of the earth.
    This is a thing which is hardly conceivable—it seems 
120
CONDITIONS AFFECTING THE
hardly imaginable—yet it  is so.   It  is indeed simply
the law of Malthus exemplified.   Mr. Malthus was a
clergyman, who worked out this subject most minutely
and truthfully some years ago ; he showed quite clearly,
—and although he was much abused for his conclusions
at the time, they have never yet been disproved and
never will  be—he showed that in consequence of the
increase in the number of organic beings in a geometri-
cal ratio, while the means of existence cannot be made
to increase in the same  ratio, that there  must come a
time when the  number  of organic beings will be in
excess of the power of production of nutriment, and that
thus some  check  must arise to the further increase of
those organic beings.   At the end of the ninth year we
have seen that each plant would  not be able  to get its
full square foot of ground, and at the end of another
year it would have to share that space with fifty others
the produce of the seeds which it would give off.
   What, then, takes  place ?  Every  plant grows up,
flourishes, occupies its  square foot of ground,  and gives
off its fifty seeds ; but notice this, that out  of this num-
ber only one can come to anything ; there  is  thus, as it
were, forty-nine chances to one against its  growing up ;
it depends upon  the  most fortuitous circumstances
whether any one  of these fifty seeds shall  grow up and
flourish, or whether  it  shall die and perish.  This is
what Mr. Darwin has drawn attention to, and called the
" Struggle for  Existence ;"  and I  have taken this
simple case of a plant because some people imagine that
the phrase seems  to imply a sort of fight.
    I have taken this plant and shown you that this is
the result of the ratio of the increase, the  necessary re-
sult of the arrival of  a  time  coming for  every species 
           PERPETUATION  OF  LIVING BEINGS.        121

when exactly as many members  must be destroyed as
are born ;  that is  the inevitable ultimate result of the
rate of production.   Now, what is the result of all this \
I have said that there are forty-nine struggling against
every one;  and it  amounts  to this, that the  smallest
possible start given  to any  one  seed  may  give  it an
advantage which will enable it to get ahead of all the
others ; anything that will enable any one of these seeds
to germinate  six hours before any of the others will,
other things being  alike,  enable  it to  choke them out
altogether.  I have show  you that there is no particu-
lar in which plants  will not vary from each other ;  it is
quite possible that one of our imaginary plants may
vary in such a character as the thickness of the integu-
ment of its seeds.   It might happen  that  one of the
plants might  produce seeds  having a thinner integu-
ment, and that would enable the seed of that plant to
germinate  a little  quicker  than those  of any of the
others,  and those seeds would most  inevitably  extin-
guish the  forty-nine times  as many that were  strug-
gling with them.
    I have  put it in this way, but you see the practical
result of the process is the same  as if some person had
nurtured the one and destroyed the other seeds.   It does
not matter how the variation is produced, so long as it
is  once allowed to  occur.   The variation in the plant
once  fairly  started, tends to  become  hereditary  and
reproduce itself; the seeds would spread themselves in
the same  way and  take part in  the struggle with the
forty-nine hundred, or forty-nine thousand, with which
they might be exposed.   Thus, by degrees,  this variety,
with some slight organic  change or modification, must
spread itself over the whole surface  of the habitable
         6 
122         CONDITIONS AFFECTING THE

globe, and  extirpate or replace the other kinds.  That
is what is  meant by  Natural Selection ;  that is the
kind of argument by which it is perfectly demonstrable
that the conditions of existence may play exactly the
same part for natural  varieties  as man does for domesti-
cated varieties.  No one doubts at all  that particular
circumstances may be more favorable for one plant and
less so  for another, and the moment you admit that, you
admit the selective power of nature.   Now,  although I
have been putting a hypothetical case, you must not
suppose  that  I  have been reasoning  hypothetically.
There are plenty of direct experiments which  bear out
what we may call the theory of natural selection ; there
is extremely good authority for the statement that if you
take the seed of mixed varieties of wheat and sow it,
collecting the seed next  year  and sowing it again, at
length  you will find that out of all your varieties, only
two or three  have lived, or perhaps even only  one.
There were one or two varieties which were best fitted
to get on, and they have  killed out the other  kinds in
just the same way and with just the same certainty as
if you  had  taken the trouble to remove them.  As I
have already said, the operation of nature is exactly the
same as the artificial operation of man.
   But if this be true of that simple case, which I put
before you, where there is nothing but the rivalry of one
member  of a species  with  others, what must be the
operation of selective conditions, when you recollect as
a matter  of fact, that for  every species of animal or
plant there are fifty or a  hundred species which might
all,  more or less, be comprehended in the same climate,
food, and station ;—that every plant has multitudinous
animals which prey upon it, and which are its direct 
           perpetuation of living beings.        123

opponents ;  and that these have other animals preying
upon them,—that every plant has its indirect helpers in
the birds  that  scatter  abroad its seed, and the animals
that  manure it with their dung;—I say, when these
things are  considered, it seems impossible that  any
variation  wliich may arise in a species in nature should
not  tend  in some  way  or other, either to  be a little
better or worse than the  previous stock ; if it is a little
better it will have an advantage over and tend to extir-
pate the latter in this crush and struggle ;  and if it is a
little worse it will itself be extirpated.
   I know  nothing that more appropriately expresses
this, than the phrase, " the struggle for existence ; " be-
cause it  brings before your minds, in a vivid sort of
way, some of the simplest possible circumstances con-
nected with it.   When a struggle is intense, there must
be some who are sure to be trodden down, crushed, and
overpowered by others;  and there will be  some who
just  manage to get through only by the help of the
slightest accident.   I recollect reading an account of the
famous  retreat of the  French troops, under  Napoleon,
from Moscow.   Worn out, tired, and dejected, they at
length came  to a great river over wliich there was  but
one bridge for the passage of the vast army.  Disorgan-
ized  and demoralized as  it was, the struggle  must cer-
tainly have been a terrible one—everyone heeding only
himself, and crushing  through and treading down his
fellows.  The writer of the narrative, who  was himself
one of those who were fortunate enough to  succeed in
getting  over, and not  among the  thousands  who were
left behind or forced into  the river, ascribed  his escape
to the fact  that he saw striding  onward  through the
mass a great strong fellow,—one of the French Cuiras- 
124:           CONDITIONS AFFECTING THE
siers,  who had  on a  large  blue  cloak—and he  had
enough presence of mind to catch and retain a hold of
this strong man's  cloak.  He says, " I caught hold of
his cloak, and although he swore at me and cut at  and
struck me by turns, and at last, when he  found he could
not shake me off, fell to entreating me to leave go  or I
should prevent him from escaping,  besides not assisting
myself, I still  kept tight  hold of  him,  and would not
quit my grasp until he had at last dragged me through."
Here  you see was a case of selective saving—if we may
so term it—depending for its success on the strength of
the cloth of the  Cuirassier's  cloak.  It is the same in
nature ;  every species has its Beresina;  it has to fight
its way through  and  struggle with other species;  and
when  well  nigh  overpowered,  it  may be that  the
smallest chance, something in its colour, perhaps—the
minutest circumstance—will  turn the  scale one way or
the other.
   Suppose that by a variation of the black race it  had
produced the white man at  any time—you know  that
the Negroes are said to believe this to have been the
case, and to imagine that Cain was the first white man,
and that we are his descendants—suppose that this had
ever  happened,  and  that the first residence of  this
human being was on  the West Coast of Africa.   There
is no great structural difference between the white man
and the  Negro, and yet there is something so singularly
different in the constitution of the two, that the malarias
of that country, which do not hurt the black at all, cut
off and  destroy the white, thus you  see there  would
have been a selective operation performed.   If the white
man had risen in that way, he would have been selected
out and removed by means of the malaria.  Now there 
PERPETUATION OF LIVING BEINGS.        125
 really is a very  curious case of selection of this  sort
 among pigs, and it is a case of selection of colour,  too.
 In the woods of Florida there are a great many pigs,
 and it is a very curious thing that they are all  black,
 every one of them.  Professor Wyman was there some
 years ago, and on noticing no pigs but these black ones,
 he asked some  of the people how  it was  that they
 had no white pigs, and the reply was that in the woods
 of Florida  there was  a root which they called  the
 Paint Hoot, and that if the white pigs were  to eat  any
 of it, it had the effect of making  their hoofs crack,  and
 they died, but if the black pigs eat any of it, it did not
 hurt them  at  all. Here was a very  simple  case of
 natural selection.  A skilful breeder could not more
 carefully develop the black breed of pigs, and weed  out
 all the white pigs, than the Paint Eoot does.
    To show you how remarkably indirect may be such
 natural selective agencies as  I have referred to, I  will
 conclude by noticing a case mentioned by Mr. Darwin,
 and which is certainly one of the most curious of its
 kind.  It is that of the  Humble  Bee.  It has been
 noticed that there are a great many more  humble bees
 in  the neighbourhood of towns, than out  in the open
 country ;  and the  explanation of the matter is this :  the
 humble bees build nests, in which they store their honey
 and deposit the larvae  and  eggs.  The field mice are
 amazingly fond of the honey and  larvae;  therefore,
 wherever there are plenty of field mice,  as  in the coun-
 try, the humble bees are kept down ;  but  in the neigh-
 bourhood of towns,  the  number  of cats  which prowl
 about the fields eat up the field mice, and of course  the
 more mice they eat up the less there are to prey upon
the larvae of the bees—the  cats are therefore the indi- 
126
CONDITIONS, etc.
rect helpers of the bees.*  Coming back a step farther
we may say that the old maids are also indirect friends
of the humble bees, and indirect  enemies  of the field
mice, as they keep the  cats which  eat  up the latter!
This is an illustration somewhat  beneath the dignity of
the subject, perhaps, but it occurs to me in passing, and
with it I will conclude this lecture.

   * The humble bees, on  the other hand, are direct helpers of
some plants, such as the heartsease and red clover, which are
fertilized by the visits of the bees ; and they are indirect helpers
of the numerous insects which are more or less completely sup-
ported by the heartsease and red clover. 
LECTUEE  VI.
A  CRITICAL EXAMINATION  OF  THE  POSITION OF
    MR.  DARWIN'S  WORK,  "ON  THE  ORIGIN OF
    SPECIES,"  IN  RELATION   TO  THE  COMPLETE
    THEORY OF  THE  CAUSES OF THE  PHENOME-
    NA  OF  ORGANIC  NATURE.

   In the preceding five lectures I have endeavoured to
give you an account of those facts, and of those reason-
ings from facts, which form  the data  upon which  all
theories regarding the causes of the phenomena of or-
ganic nature must be based.   And, although I have had
frequent occasion to quote Mr. Darwin—as all  persons
hereafter, in speaking upon these subjects, wTill have
occasion to  quote his famous book on the " Origin of
Species,"—you must  yet remember that,  wherever I
have  quoted him,  it has  not been upon theoretical
points, or for statements in any way connected with his
particular speculations, but on matters of fact, brought
forward by  himself, or collected by himself, and which
appear incidentally in his book.  If a man will  make
a book, professing to discuss a  single  question, an en-
cyclopaedia,  I cannot help it.
    Now, having had  an opportunity of considering in
this sort of way the different statements bearing upon
all  theories  whatsoever, I have to-night to lay before 
128           MR. darwin's work and

you, as fairly as I can, what is Mr. Darwin's view of the
matter and what position his theories hold, when judged
by the principles which I have previously laid down as
deciding our judgments upon all theories and hypotheses.
   I have already stated to you that the inquiry respect-
ing the causes of the  phenomena of organic nature re-
solves itself  into two  problems—the first being  the
question of the origination of living or organic beings;
and the second being  the totally distinct problem  of the
modification  and perpetuation of organic beings when
they have already come into existence.  The first ques-
tion Mr. Darwin does not touch ; he does not deal with
it at all; but he says—given the origin of organic mat-
ter—supposing its creation to have already taken  place,
my object is  to show in consequence of what  laws  and
what demonstrable properties of organic matter, and of
its environments, such states of organic nature as those
with which we are  acquainted must have come about.
This, you will observe, is a perfectly legitimate propo-
sition ; every person has a right to define  the limits of
the inquiry which he sets before himself; and yet  it is
a most  singular thing that in all the multifarious,  and
not unfrequently, ignorant attacks which have been made
upon the " Origin of Species," there is nothing which has
been more speciously criticised than this particular limi-
tation.   If people have  nothing else to urge against the
book, they say—" Well, after all, you see Mr.  Darwin's
explanation  of the  ' Origin of Species' is  not good for
much, because, in the long run, he admits that he does
not know  how organic  matter began to exist.  But if
you admit  any special  creation for the first particle of
organic  matter you  may just as well admit it for all the
rest;  five hundred or  five thousand distinct creations 
         the phenomena of organic nature.      129

are just as intelligible,  and just as little  difficult to
understand, as one."   The  answer to these cavils is
two-fold.   In  the first place, all human  inquiry must
stop somewhere;  all our knowledge and  all our inves-
tigation cannot take us  beyond the limits set  by the
finite and restricted character of our faculties, or de-
stroy the endless unknown,  which accompanies, like
its  shadow, the endless  procession  of phenomena.  So
far as I  can  venture to offer  an  opinion  on such a
matter, the  purpose of our being in existence,  the
highest object that human beings can set before them-
selves, is  not  the pursuit of any such  chimera as the
annihilation of the unknown; but  it is simply the un-
wearied endeavour  to remove its  boundaries a little
further  from our little sphere of action.
    I wonder if any historian would  for a moment admit
the objection, that it is preposterous to trouble ourselves
about the history of the  Roman Empire, because we do
not know anything positive about  the origin and first
building of the city of Pome !   Would it be a fair ob-
jection to urge respecting the sublime  discoveries of a
Newton, or a  Kepler, those great  philosophers, whose
discoveries have  been of the profoundest benefit  and
service  to all men,—to  say to them—" After all  that
you have told us as to how the planets revolve, and how
they are maintained in their orbits, you cannot tell us
what  is the cause of the origin of  the  sun, moon, and
stars.   So what is the use of what you have done ?"
Yet these objections would not be  one whit more pre-
posterous than the objections which  have been made to
the " Origin of Species."   Mr.  Darwin,  then, had a
perfect right to limit his inquiry as  he pleased, and the
only question for us—the inquiry being so limited—is
         6* 
130
MR. DARWIN'S WORK AND
to ascertain whether the method of his inquiry is sound
or unsound; whether he has obeyed the  canons which
must guide and govern all investigation, or whether he
has broken them;  and it was because our inquiry this
evening is essentially limited  to  that  question that I
spent a good  deal of time in  a former lecture (which,
perhaps some  of you thought might have been better
employed) in endeavouring to illustrate the method and
nature of scientific inquiry in  general.  We shall now
have to put in practice the principles that I then laid
down.
    I stated  to you in substance, if not in words, that
wherever there are complex masses of phenomena to be
inquired into, whether they be phenomena of the affairs
of daily life, or whether they belong to the more abstruse
and difficult problems laid before the philosopher, our
course of proceeding in unravelling that complex chain
of phenomena with a view to get  at its cause, is always
the same; in all cases we must invent a hypothesis;  we
must place  before ourselves some more  or less likely
supposition  respecting that cause;  and then,  having
assumed  a hypothesis, having supposed a cause for the
phenomena in question,  we must endeavour, on  the one
hand, to demonstrate our hypothesis, or, on the other, to
upset  and reject it  altogether, by testing it in three
ways.  We  must, in the first place,  be prepared  to
prove  that  the  supposed causes  of  the phenomena
exist in   nature;  that they  are  what the logicians
call vera causa—true causes;—in the next  place, we
should be prepared to show that  the assumed causes of
the phenomena are  competent to produce such pheno-
mena  as  those which we wish to  explain by them ;  and
in  the last place, we ought to  be able to show  that no 
         the phenomena of organic nature.     131

other known causes  are  competent to produce  these
phenomena.   If we  can succeed  in  satisfying  these
three conditions, we shall have demonstrated our hypo-
thesis ;  or rather I  ought to say, we shall have proved
it as far as certainty is possible for us; for, after  all,
there is no one of our surest convictions which may not
be upset, or at any  rate modified by a further accession
of knowledge.   It  was because it  satisfied these con-
ditions  that we accepted the  hypothesis as to the dis-
appearance of the tea-pot and spoons in the case I sup-
posed in a previous lecture; we found that our  hypo-
thesis on that  subject was  tenable and valid,  because
the supposed cause existed in nature, because it was
competent  to account for the phenomena,  and  because
no  other known cause was competent to  account for
them; and it  is upon similar  grounds that any  hypo-
thesis you  choose  to name is accepted in science  as
tenable and valid.
    What is Mr. Darwin's hypothesis ?   AT I apprehend
it—for I have put it into  a  shape more convenient for
common purposes than I could find verbatim in his book
—as I apprehend it, I say,  it is, that all the phenome-
na  of  organic nature, past and  present, result  from,
or are caused by, the inter-action of those properties of
organic matter, which  we  haye called  Atavism and
Variability, with  the  Conditions of Existence ; or,
in other words,—given the existence of organic matter,
its tendency to  transmit its properties, and its tendency
occasionally to vary;  and, lastly, given the conditions
of existence by which organic  matter is surrounded—
that these put  together are the causes of  the Present
and of the Past conditions of Organic Nature.
    Such is the  hypothesis as  I understand it.  Now 
132            me.  darwin's work and

let us see how it will stand the various tests which I laid
down just now.  In the first place, do these supposed
causes  of the  phenomena exist  in  nature ?  Is it  the
fact  that in nature these properties of organic  matter
—atavism and variability—and those phenomena which
we have called the conditions of existence,—is  it true
that  they exist % -  Well, of course, if they do not exist,
all that I have told you in  the last three  or four lec-
tures must be incorrect, because I have been attempting
to prove that they do exist,  and I take it that there is
abundant evidence that they do exist;  so far, therefore,
the hypothesis does not break down.
   But in the  next place comes a much more difficult
inquiry:—Are  the  causes indicated competent  to give
rise  to the phenomena of organic nature ?   I  suspect
that  this is indubitable to  a certain extent. It is de-
monstrable,  I  think,  as  I have endeavoured to show
you,  that they are perfectly competent to give rise to all
the phenomena wdiich are exhibited by Racks-in nature.
Furthermore, I believe that they are  quite competent
to account for  all that we  may call purely structural
phenomena  which are exhibited by  Species in nature.
On that point also I have already enlarged somewhat.
Again, I think that the causes assumed are competent
to account for most of the physiological characteristics
of species, and I not only think that they are competent
to account for them, but I think that  they account for
many things which otherwise remain wholly unaccount-
able  and inexplicable, and I  may say incomprehensible.
For  a full exposition of the  grounds on which this con-
viction  is based,  I must refer  you to Mr. Darwin's
work ;  all that I can do now is to illustrate what I have
said by two or three cases taken  almost at random. 
        THE PHENOMENA OF ORGANIC NATURE.     133

   I drew your attention, on a previous evening, to the
facts which are embodied  in  our systems  of  Classifi-
cation, which  are the results  of the examination and
comparison  of the  different  members of the animal
kingdom one  with another.    I  mentioned that the
whole of the animal kingdom  is divisible into five sub-
kingdoms ;   that each of these sub-kingdoms is  again
divisible into  provinces;  that each province  may be
divided into classes, and the classes into the successively
smaller groups, orders, families, genera, and species.
   Now, in each of these  groups, the resemblance in
structure among the members  of the group is closer in
proportion  as  the group is smaller.  Thus, a man and
a worm are members of the animal kingdom in virtue
of certain apparently slight though  really fundamental
resemblances which they present.   But a man and a
fish are members of the same Sub-kingdom  Vertebrata,
because they  are much  more  like one  another than
either of them is to a worm, or a snail, or any member
of the other sub-kingdoms.   For similar reasons men
and  horses  are arranged as members of the  same  Class,
Mammalia / men and  apes as members of the same
Order, Primates / and if there were any animals more
like men than they were like  any of the apes, and yet
different from men  in important and constant  particu-
lars  of their  organization, we should rank them as
members of the same Family, or of the same Genus,
but as of distinct Species.
   That it  is possible to  arrange all the varied forms of
animals into groups, having this sort of singular subor-
dination one to the other, is a very remarkable  circum-
stance ; but, as Mr. Darwin remarks, this  is a result
which is quite to be expected, if the principles which he 
134
mr. darwin's work and
 lays down be correct.   Take the case of the races which
 are known to be produced by the operation of atavism
 and variability, and the conditions  of existence  wliich
 check and modify these tendencies.   Take the case of
 the pigeons that  I brought before  you :  there  it was
 shown that  they might be all  classed as belonging to
 some  one of five principal divisions, and that within
 these  divisions  other  subordinate  groups  might  be
 formed.  The members of these groups are  related to
 one another in just the same way as the genera of a
 family, and the groups themselves as the families of an
 order, or the orders of a class; while all have the same
 sort of structural relations with the wild  Rock-pigeon,
 as the members of any great natural group have with a
 real or imaginary typical  form.   Now, we know that
 all varieties of pigeons  of every kind have arisen by a
 process of selective breeding from  a common stock, the
 Rock-pigeon ; hence, you see, that if  all species of ani-
 mals have proceeded from some common stock, the gen-
 eral character of their  structural  relations, and of  our
 systems of classification, which express those relations,
 would be just what  we find them  to be.   In  other
 words, the hypothetical cause is, so far, competent to
 produce effects similar to those of the real cause.
    Take, again, another set of very remarkable facts,—
 the  existence of what are  called  rudimentary organs,
 organs for which we  find  no obvious use, in  the par-
 ticular animal economy in which  they are found, and
 yet which are there.
    Such are the splint-like bones in the leg of the
horse, which  I here show  you,  and  which correspond
with bones wliich belong  to certain toes  and fingers
in the human hand and foot.   In the horse you see 
         THE PHENOMENA OF  ORGANIC NATURE.     135

they are quite rudimentary, and bear neither toes nor
fingers;  so that the horse has  only one " finger"  in
his fore-foot and one " toe"  in his hind-foot.  But it
is a very curious thing that  the animals closely allied
to the horse show more toes than he ; as the rhinoceros,
for instance : he has these extra toes well formed, and
anatomical facts show very clearly that he is very closely
related  to the horse indeed.   So we may say that ani-
mals, in  an anatomical  sense  nearly  related  to  the
horse, have those parts which are  rudimentary in him,
fully developed.
    Again, the sheep and the  cow have no cutting-teeth,
but  only a hard pad in the upper  jaw.   That is  the
common characteristic of ruminants in  general.  But
the calf has in its upper jaw some rudiments of teeth
which never are developed,  and never  play the part
of teeth at all.   Well, if you  go back in time, you find
some of the older, now extinct, allies of the  ruminants
have well-developed teeth in their upper  jaws ; and at
the present day the pig (which is in structure closely
connected with ruminants) has well-developed teeth in
its  upper jaws ;  so  that  here is  another instance  of
organs well developed and very useful, in one animal,
represented by  rudimentary organs,  for which we can
discover no  purpose whatsoever,  in another  closely
allied animal.   The whalebone whale, again, has horny
" whalebone " plates in its mouth, and no teeth ; but
the young fcetal whale, before it is  born, has teeth  in
its jaws ; they, however, are never  used, and they never
come to anything.   But other members of the group to
which the whale belongs have well-developed teeth  in
both jaws.
   Upon any hypothesis of special  creation, facts of this 
136           mr.  darwin's work and

kind appear  to  me to  be entirely unaccountable and
inexplicable, but they cease  to  be so if you accept Mr.
Darwin's hypothesis, and  see reason for believing that
the whalebone whale and the whale with teeth in its
mouth both sprang from a whale that had teeth, and
that  the teeth of the fcetal whale are merely remnants
—recollections, if we may so say—of the extinct whale.
So in the case of the horse and the rhinoceros : suppose
that  both have descended by modification from  some
earlier form which had the normal number of toes, and
the persistence of  the  rudimentary bones  which no
longer support  toes in  the  horse becomes  compre-
hensible.
    In the language that we speak in England, and in
the language of the Greeks, there are identical verbal
roots, or elements  entering  into  the  composition of
words.  The  fact remains unintelligible so long as we
suppose English and Greek to be independently created
tongues ; but when  it is shown that both languages are
descended. from one original, the Sanscrit, we give an
explanation of that  resemblance.  In the same way the
existence of identical structural roots, if I may so term
them, entering into the composition of widely different
animals, is  striking  evidence in  favour of the  descent
of those animals from a common original.
   To turn to another kind of illustration:—If you
regard the  whole series of stratified rocks—that  enor-
mous thickness of sixty or seventy thousand  feet  that
1 have mentioned before, constituting the only record
we have of a most  prodigious lapse of time, that time
being, in all probability, but a fraction of that of which
we have no record ;—if you observe in these successive
strata of rocks successive groups of  animals arising and 
         THE PHENOMENA OF ORGANIC NATURE.      137

dying out, a constant  succession, giving you the  same
kind of impression, as you travel from one group of
strata to another, as you would have in travelling  from
one country to another ;—when you find this constant
succession of forms, their traces obliterated except to
the man of science,—when you look at this wonderful
history, and  ask what it  means, it is  only a paltering
with words if you  are offered the reply,—" They were
so created."
    But if, on the other hand, you look on all forms of
organized beings as the results of the  gradual  modifi-
cation of a primitive type, the facts receive a meaning,
and you see that these older conditions are the necessary
predecessors of the present.  Viewed  in this light the
facts of palaeontology receive a meaning—upon  any
other hypothesis, I am unable to see, in the slightest
degree, what knowledge or signification we are to draw
out  of them.   Again, note as bearing  upon the same
point, the singular likeness which obtains between the
successive  Faunas  and Floras, whose remains are pre-
served  on the rocks:  you never find any great  and
enormous difference between the immediately successive
Faunas  and Floras, unless you have reason to  believe
there has also been a great lapse of time or  a great
change  of conditions.   The animals, for instance, of the
newest  tertiary rocks,  in  any part of the world, are
always, and without exception, found to be closely allied
with those which now live in that part  of the world.
For  example, in Europe,  Asia, and Africa, the large
mammals are at present rhinoceroses,  hippopotamuses,
elephants, lions, tigers, oxen, horses, &c. ; and  if you
examine the newest tertiary deposits, which contain the
animals and  plants wliich  immediately preceded those 
138
MR. DARWIN'S WORK AND
which now exist in the same country, you do not find
gigantic specimens of ant-eaters and kangaroos, but you
find rhinoceroses, elephants, lions, tigers, &c,—of differ-
ent species to those now living,—but still their  close
allies.  If you  turn to South America, where,  at the
present  day, we have great sloths and armadilloes and
creatures of that kind, what do  you find in the  newest
tertiaries ?  You find the  great  sloth-like creature, the
Megatherium, and the great armadillo, the Glyptodon,
and so on.   And if you go to Australia you find the
same law holds  good, namely, that that condition of or-
ganic nature which has preceded the one which now
exists, presents differences perhaps of species, and of
genera, but that the great types of organic structure
are the same as those which now flourish.
    What meaning  has this fact upon any other hypo-
thesis or supposition than one of successive modifica-
tion ?  But if the  population of the world, in any age,
is  the result of the gradual modification of  the forms
which peopled it in the preceding age,—if that has been
the case, it is intelligible enough ; because we may ex-
pect that the creature that results from the modification
of an elephantine mammal shall  be  something  like an
elephant, and the  creature which is  produced  by the
modification of  an armadillo-like mammal shall  be like
an  armadillo.   Upon that supposition, I say, the  facts
are intelligible; upon any other, that I am aware of,
they are not.
    So far, the facts of palaeontology are consistent with
almost any form of the doctrine of progressive  modifi-
cation ;  they would not be absolutely inconsistent with
the wild speculations  of De Maillet,  or with the less
objectionable hypothesis of Lamarck.  But  Mr.  Dar- 
         THE PHENOMENA OF ORGANIC NATURE.      139

win's views have one  peculiar merit; and that is, that
they are perfectly consistent with an array of facts which
are utterly inconsistent with  and fatal to,  any other
hypothesis of progressive modification which has yet
been  advanced.  It is one remarkable peculiarity of
Mr. Darwin's hypothesis that  it involves no necessary
progression or incessant modification,  and  that it  is
perfectly consistent with  the persistence for any length
of time of a given primitive stock,  contemporaneously
with  its modifications.  To return  to  the case  of the
domestic breeds of pigeons, for example ; you have the
Dove-cot  pigeon,  which closely  resembles  the Rock
pigeon, from wliich they all  started,  existing  at the
same  time with the others.  And if species are devel-
oped  in the same way  in nature, a primitive stock and
its modifications may,  occasionally, all find the con-
ditions  fitted for  their existence;  and though they
come into competition, to  a  certain extent, with  one
another, the  derivative species may not necessarily ex-
tirpate the primitive one, or vice versa.
   Now palasontology shows us many  facts  which are
perfectly harmonious with these observed effects of the
process by which Mr. Darwin supposes  species to have
originated, but which  appear  to me to be  totally in-
consistent  with any other  hypothesis which  has been
proposed.   There  are some groups  of animals  and
plants,  in  the  fossil world, which  have been  said to
belong  to  " persistent  types," because they have per-
sisted, with very little  change indeed,  through a very
great range of time, while everything  about them has
changed largely.  There are families  of fishes whose
type of construction has persisted all the way from the
carboniferous  rock right up  to the cretaceous;  and 
140           me.  darwin's work and

others  which  have lasted through almost the whole
range of the secondary rocks, and  from the lias to the
older tertiaries.   It is something stupendous this—to
consider a genus lasting without essential modifications
through all  this enormous lapse  of time while almost
everything else was changed and modified.
   Thus I have no doubt that Mr. Darwin's hypothesis
will  be found competent to  explain  the majority  of
the phenomena exhibited by species in nature; but in
an earlier lecture I spoke cautiously with repect to  its
power  of explaining all the physiological peculiarities
of species.
   There is, in fact, one set of these peculiarities which
the  theory of selective modification,  as it  stands  at
present, is not wholly competent to explain, and that is
the group of  phenomena which I mentioned to you
under  the name of Hybridism, and which I explained
to consist in the sterility of the offspring of certain spe-
cies when crossed one with another.  It matters not one
whit whether  this  sterility is universal, or whether it
exists only in a single case.  Every hypothesis is bound
to explain, or, at  any rate, not be  inconsistent with, the
whole of the facts which it professes to  account for ; and
if there is a single one of these facts which can be shown
to be inconsistent with (I do not merely mean inexpli-
cable by, but contrary to,) the hypothesis, the hypothesis
falls to the ground,—it is worth nothing.   One fact with
which  it is positively inconsistent is worth as much, and
as powerful in negativing the hypothesis, as five hun-
dred.  If I  am right in thus defining the obligations of
a hypothesis, Mr.  Darwin, in order to place his views
beyond the reach  of all  possible assault, ought to  be
able to demonstrate the possibility of developing from 
THE PHENOMENA OF ORGANIC NATURE.     141
a particular  stock  by selective breeding, two  forms,
wliich  should  either be  unable  to cross  one with
another, or whose cross-bred offspring should be infer-
tile with one another.
   For, you see, if you have not done that you have not
strictly fulfilled all  the conditions of the  problem ; you
have not  shown that you  can  produce, by  the cause
assumed, all  the phenomena wliich you have  in nature.
Here are  the phenomena of Hybridism staring you  in
the face,  and you cannot say,  " I can, by selective
modification, produce these same  results."  Now, it is
admitted on all  hands that, at present, so far as experi-
ments  have gone, it has not been found possible to pro-
duce this complete physiological divergence by selective
breeding.   I stated this very clearly before, and I now
refer to the  point, because, if it could  be proved, not
only that  this has not been done,  but that it cannot  be
done ;  if it could be demonstrated that it is impossible
to breed selectively, from any stock, a form which shall
not breed with another, produced  from the same stock;
and if we were shown  that this must be the necessary
and  inevitable result of all experiments, I  hold  that
Mr. Darwin's hypothesis would be utterly shattered.
   But has this been done ? or what is really the state
of the case ?   It is simply that, so far as we  have gone
yet with  our breeding, we have not produced from a
common stock two breeds which  are not more or less
fertile  with one another.
   I do not know  that there is  a single fact which
would justify any one in saying that any degree  of ster-
ility has  been  observed  between breeds  absolutely
known to have been produced  by selective breeding
from a common stock.  On the  other hand, I do not 
142
MR. DARWIN'S  WORK AND
know that there is a single  fact which can justify any
one in asserting that such sterility cannot be produced
by proper experimentation.   For my own part, I  see
every reason to believe  that it may,  and will be so pro-
duced.  For, as Mr. Darwin has very properly urged,
when we  consider the phenomena of sterility, we find
they are most  capricious;  we do not know what it is
that the sterility depends on.   There are some animals
which will  not breed in captivity; whether it  arises
from the simple fact of their being shut up and deprived
of their liberty,  or not, we do not know,  but they
certainly  will not breed.  What an astounding  thing
this is, to  find one of the most important of all functions
annihilated by mere imprisonment!
   So, again, there are cases known of animals which
have been thought  by naturalists to be undoubted spe-
cies,  which  have yielded fertile  hybrids; while  there
are other species which present what everybody believes
to be varieties* which  are more or  less  infertile with
one  another.   There are other  cases wliich  are truly
extraordinary;  there is one,  for example,  which has
been  carefully examined,—of two  kinds of sea-weed,
of which  the male  element of the one, wliich we may
call A, fertilizes the female  element of the  other, B ;
while the male element of B will not fertilize the female
element  of A; so that, while the  former experiment
seems  to  show us  that they are varieties, the  latter
leads to the conviction that they are species.

   *  And as I conceive with very good reason ; but if any objec-
tor urges that we cannot prove that they  have been produced by
artificial or natural selection, the objection must be admitted—
ultra-sceptical as it is.  But in science, scepticism is a duty. 
         THE PHENOMENA OF ORGANIC NATURE.      143

   When we see how capricious  and uncertain this
sterility is, how  unknown the  conditions on which  it
depends, I say that  we have  no right to affirm  that
those conditions will not be better understood by and
by, and we have no ground  for supposing that we may
not be able to experiment so  as to obtain that crucial
result which  I mentioned just now.   So that though
Mr. Darwin's hypothesis does  not completely extricate
us from this difficulty at present, we have not  the least
right to say it will not do so.
    There is  a wide  gulf between the thing you cannot
explain  and  the thing that   upsets  you  altogether.
There is  hardly any hypothesis in this  world  which
has not some fact in connection with it wliich has not
been  explained, but  that is  a  very different affair to a
fact that entirely opposes your hypothesis ; in  this case
all you can say is, that your hypothesis  is in the same
position as a good many others.
   Now, as to the third test, that there are  no other
causes competent to explain the phenomena, I explained
to you  that one should be able to say of a hypothesis,
that no other known causes than those supposed by it
are competent to give rise  to  the  phenomena.  Here,
I think, Mr. Darwin's view is pretty strong.  I really
believe  that the alternative  is  either Darwinism  or
nothing, for I do not know of any rational conception
or theory of the organic universe which  has any scien-
tific position  at  all beside  Mr.  Darwin's.   I do not
know of any proposition that has  been  put before  us
with  the intention  of explaining  the phenomena of
organic nature,  which  has  in its  favor  a thousandth
part of  the  evidence which  may be adduced in  favour
of Mr. Darwin's views.  Whatever may be the objec- 
144
MR. DARWIN'S WORK AND
 tions to his views, certainly all others are absolutely out
 of court.
    Take the Lamarckian hypothesis, for example.  La-
 marck was a great naturalist, and to a certain  extent
 went the right way to work ; he argued from what was
 undoubtedly a true cause of some of the phenomena of
 organic nature.  He said it is  a  matter of  experience
 that an animal may be modified more or less in  conse-
 quence of  its desires and consequent actions.  Thus if
 a man  exercise himself as  a blacksmith, his arms will
 become strong  and muscular;  such organic modifica-
 tion is a result of this particular action and exercise.
 Lamarck  thought  that by  a very simple supposition
 based on this truth he could explain the oirgin of the
 various animal species:  he said, for example, that the
 short-legged birds which live on fish, had been converted
 into the long-legged waders by desiring to get the fish
 without wetting their feet, and  so stretching their legs
 more  and  more  through successive  generations.  If
 Lamarck could have shown experimentally,  that  even
 races of animals could be produced  in  this way, there
 might  have  been some ground for his speculations.
 But he could show nothing of the  kind, and his hy-
pothesis has pretty well dropped into oblivion, as  it de-
served to do.  I said in an earlier lecture that there are
hypotheses and  hypotheses, and when people tell you
that.Mr. Darwin's strongly-based hypothesis  is nothing
but a mere modification of Lamarck's, you  will  know
what to think of their capacity for forming a  judgment
on this subject.
   But  you must recollect that when  I say  I think it
is  either Mr. Darwin's hypothesis  or  nothing;  that
either we must take his view, or look  upon  the'whole 
         THE PHENOMENA OF ORGANIC NATURE.     145

of organic nature  as an enigma, the meaning of which
is wholly hidden from us ;  you must understand that I
mean that I accept it provisionally, in exactly the same
way as  I accept any other hypothesis.  Men of science
do not pledge themselves to creeds ; they are bound by
articles  of no sort; there  is not a single belief that it
is not a bounden duty with them to hold with a light
hand and to part  with it,  cheerfully, the moment  it is
really proved to be contrary to any fact, great or small.
And  if in course of time I see good reasons for such a
proceeding,  I shall have no hesitation in coming before
you, and pointing out any change in my opinion without
finding  the slightest occasion to blush for so doing.  So
I say that we accept this view as we accept any other,
so long  as it will help us, and we feel bound to retain it
only so  long as it will serve  our  great purpose—the
improvement of Man's estate and  the widening of his
knowledge.   The moment this, or any other  conception,
ceases to be  useful for these purposes, away with it  to
the four winds ; we care not what becomes of it!
   But  to say truth, although  it has been my business
to attend closely  to  the  controversies roused  by the
publication of Mr. Darwin's book, I think that  not one
of the enormous mass of objections and obstacles which
have  been raised  is of any great value,  except  that
sterility  case which I  brought before you  just now.
All the  rest are misunderstandings of some sort, arising
either from  prejudice, or want of knowledge,  or still
more from want of patience and care in reading the
work.
   For  you  must  recollect that it  is not a book to be
read with as much ease as its pleasant style may lead
you to imagine.   You spin through  it as  if it were  a
         7 
146
MR. darwin's work and
 novel the first time you read it, and think you know all
 about it;  the second time you read it you think you
 know rather less about it; and the third time, you are
 amazed to find  how little you have really apprehended
 its vast scope and objects.  I can positively say that I
 never take it up without finding in it some new view
 or light, or suggestion that I have not noticed before.
 That is the  best characteristic of a thorough and pro-
 found book ;  and I believe this feature of the " Origin
 of Species"  explains  why so many persons have  ven-
 tured to pass judgment and  criticisms upon  it which
 are by no means worth the paper they are written on.
    Before concluding  these lectures there is one point
 to which I must advert,—though, as Mr. Darwin has
 said nothing  about man in his book, it concerns myself
 rather than him;—for I  have strongly maintained on
 sundry occasions that  if Mr. Darwin's views are sound,
 they apply as much to man as  to the lower mammals,
 seeing that it is perfectly demonstrable that the struc-
 tural differences  which separate man from the apes are
 not greater than those which separate some apes  from
 others.  There cannot be  the slightest  doubt in the
 world that the argument which applies to the improve-
 ment of the horse from an earlier stock,  or of ape from
 ape, applies  to  the improvement  of man from some
 simpler and  lower stock  than man.  There is not a
 single  faculty—functional or  structural, moral, intel-
lectual,  or  instinctive,—there  is no faculty whatever
that is not capable of improvement; there is no faculty
whatsoever which does not depend upon structure, and
 as structure tends to  vary, it is capable of being im-
proved.
   Well, I  have taken a good deal  of pains at various 
         THE PHENOMENA OF ORGANIC NATURE.      147

times to prove this, and I  have endeavoured to meet
the objections of those who maintain, that the structural
differences between  man and  the lower animals are of
so vast  a character and enormous extent, that even if
Mr. Darwin's views are correct, you cannot imagine this
particular  modification to  take place.   It  is, in fact,
easy matter  to prove  that, so far  as structure  is con-
cerned, man  differs to no greater extent  from the ani-
mals wliich are immediately below him  than these do
from  other members  of the  same order.  Upon the
other hand, there is no one who estimates more highly
than I do the dignity  of human  nature,  and the width
of the gulf in intellectual and  moral matters, which lies
between man and the whole of the lower creation.
    But  I  find this very  argument  brought forward
vehemently  by some.  " You say  that  man has pro-
ceeded  from a modification of some lower animal, and
you take pains to prove that  the structural differences
which are  said to exist in  his brain do not exist at  all,
and you teach that all functions, intellectual,  moral,
and others, are the expression  or the result,  in the long
run,  of structures, and of the molecular forces which
they exert."   It is quite true that I do so.
    " Well, but,"  I am told  at once, somewhat triumph-
antly, " you  say in the same breath that there is  a great
moral and intellectual chasm  between  man and  the
lower animals.  How is this possible when  you  declare
that  moral and  intellectual characteristics  depend on
structure, and yet tell us that there is no such gulf be-
tween the structure of man and that of the lower ani-
mals?"
    I think that objection is based upon a misconception
of the real relations which exist between structure and 
14:8           MR. darwin's work and
 function, between mechanism  and work.   Function is
 the expression of molecular forces and arrangements no
 doubt;  but, does it follow from this, that variation in
 function so depends upon variation in structure that the
 former is always exactly proportioned to the latter ?  If
 there  is no such relation, if the variation in  function
 which follows on a variation in structure may be enor-
 mously greater than the variation of the structure, then,
 you see, the objection falls to the ground.
    Take a couple of watches—made by the same maker,
 and as completely alike as possible ; set them upon the
 table, and the function of each—which is its rate of
 going—will be performed in the same manner, and you
 shall be able to distinguish no difference between them ;
 but let me take a  pair of pincers, and  if my hand is
 steady enough to do it, let me just lightly crush  to-
 gether the bearings of  the balance-wheel, or force to a
 slightly different angle  the teeth of the escapement of
 one of them,  and of course you know the immediate
 result will be  that the watch,  so treated, from that mo-
 ment will cease to go.   But what  proportion is there
 between the structural alteration  and the functional
 result ?  Is  it  not perfectly obvious that the alteration
 is of the minutest kind, yet that slight as it is, it has
 produced an infinite difference in the performance  of
 the functions of these two instruments ?
  ^  Well,  now,  apply  that to the present question.
 What is it that constitutes and makes man what he is ?
 What is it  but his power of language—that language
 giving him the means  of recording his experience—
 making  every generation somewhat wiser than  its
predecessor,—more in accordance with the established
order of the universe % 
         THE PHENOMENA OF ORGANIC NATURE.     149

   What is it but this power of speech, of recording
experience,  which  enables men  to be  men—looking
before and after and, in some dim sense,  understanding
the working of this wondrous universe—and which dis-
tinguishes man from the whole of the brute world ?  I
say that this functional difference is vast,  unfathomable,
and  truly infinite in its consequences ; and I say at the
same time, that it  may depend upon structural differ-
ences which shall be absolutely inappreciable to us with
our present  means of investigation.  What is this very
speech that  we are talking about ?  I am speaking to
you  at  this moment, but  if you were to alter, in the
minutest degree, the  proportion  of the nervous forces
now active in the two nerves which supply the muscles
of my glottis, I should become suddenly dumb.   The
voice is  produced only so long as the vocal chords are
parallel;  and these are parallel only so long as certain
muscles  contract with exact  equality; and that again
depends on  the equality of action of those two nerves I
spoke of.  So that a change of the minutest kind in the
structure of one of these nerves, or in the structure of
the part in which it originates, or of the supply of blood
to that part, or of one of the muscles to which it is dis-
tributed, might render all of us dumb.   But a race of
dumb men, deprived of all communication with  those
who could speak, would be little indeed removed from
the brutes.  And  the moral and  intellectual  difference
between them and ourselves  would be  practically in-
finite, though the naturalist should not be able to find
a single shadow of even specific structural difference.
   But let  me dismiss this question now, and, in  con-
clusion, let me say that you may go away with it as my
mature conviction,  that  Mr.  Darwin's  work is the 
150  .
mr. darwin's work, etc
greatest contribution which has been made to biological
science since the publication of the " Regne Animal "
of Cuvier, and since that of  the " History of Develop-
ment," of Von Baer.   I believe that if you strip it of
its theoretical part it  still remains one of the greatest
encyclopasdias of biological doctrine that any one man
ever brought forth ; and I believe that, if you take it  as
the embodiment of a hypothesis, it  is destined to be the
guide of biological and psychological speculation for the
next three or four generations. 
D. APPLETON & CO.'S PUBLICATIONS.
                           ON

THE   ORIGIN   OF   SPECIES
                            BY

           Means of Natural Selection;

                            OR,

THE  PRESERVATION  OF  FAVORED RACES

                           IN "HIE

                 STRUGGLE FOR  LIFE.

                            BY
     dH-A-IRXjES  nD-A-Pl^CVIW, .A..  TS/L.

               One Volume.  \2mo.  Cloth, $1.50.

                      ———♦♦-•------

   " His first point is to show that species are in many cases not well
defined, and that the whole order of natural history seems to be in a
state of mutation, by reason of  constant variations.  Thus even under
domestication,  important changes may be introduced by intercrossing,
by selection of the best individuals for propagation, by crossing parents
marked by however slight, but favorable peculiarities.
   "His second  point is what he terms the universal and  necessary
struggle for existence.  This follows from the high geometrical ratio
of increase  common to all beings.   If there were no  catastrophes,
any one of  the existing  species would be sufficiently numerous in a
few thousand years to cover the whole earth, to the exclusion of every-
thing else.
   " His third point is to prove that this struggle is directed by the
law of natural selection.   Even the races of domestic animals may be
constantly improved and  modified by choosing  the best individuals
for propagation.   Nature brings the same discipline to bear upon the
whole domain  of animal and vegetable life.  She seizes at once upon
any slight variation that is favorable, and perpetuates it; in the uni-
versal pressure, any variation that is injurious is immediately extin-
guished." 
D. APPLETON & CO.'S PUBLICATIONS.
                    HISTORY
                               OF

CIVILIZATION   IN   ENGLAND.

        By HENRY  THOMAS  BUCKLE.

                3  "Vols.  8vo, Cloth.   $5.
                                ♦--------

                    (From the Boston Journal.)
   " Singularly acute,  possessed of rare analytical power, imaginative but not
fanciful, unwearied in research, and gifted with wonderful talent in arranging
and moulding his material, the author is as fascinating as he is learned.   His
erudition is immense—so immense as not to be cumbersome. It is the result
of a long and steady growth—a part of himself.

                 (From tlie Chicago Borne Journal.)
   "The master-stroke of the  first volume is the author's skill and success in
delineating the train of causes which resulted  in the early French Revolution
^1793).  These causes, with their combinations, are so arranged that the mind
of the reader  is prepared for results not very unlike such as actually occurred,
horrible as they were.

                   (From  the Boston Transcript.)
   "His first volume evinces a clear head, an intrepid heart, and an honest pur-
pose. A true kind of induction characterizes it Indeed it is almost a new
revelation, comprising the fidelity of Gibbon, the comprehensiveness of Hum-
boldt, and the fascination of Macaulay."

                   (From the JV. Y. Daily Times.)
   "We have read Mr. Buckle's volumes with  the deepest interest.  We owe
him a profound debt of gratitude.  His influence on the thought of the present
age cannot but be enormous, and if he gives us no more than we already have
in the two volumes of the magnus opus, he will still be classed among the
lathers and founders of the Science of History."

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