From the American Journal of Science and Arts, Second Series, Vol. IX. 
ON THE 
SO-CALLED BIOGEN LIQUID, 
By CHARLES GIRARD, 
Member of the Boston Natural'IKstory Society. 
The following pages are devoted to an examination of a letter 
published in the American Journal of Science and Arts,* also of 
a communication read before the Boston Natural History So- 
ciety in December, 1848. f 
The letter consisted of an expose of three facts and one the- 
ory, viz.: 
First fact. The formation of the egg in the ovary, as observed 
in a soft-shelled mollusk (Ascidia) and in a worm (Sigalion). 
Second fact. The germinative vesicle does not always and 
necessarily disappear before the division of the yolk. 
Third fact. There exists in the centre of the germinative 
spot, a transparent vesicle. 
Theory. What embryologists have called albumen in the egg 
of invertebrated animals, has nothing in common with the albu- 
men of the egg of Vertebrata. This liquid is the mother liquid 
of the yolk, that is to say, of the elements from which a new 
individual originates; therefore it is called Biogen. 
These facts which have been added to science were not first 
made known by Mr. Desor. The theory is really his own. We 
shall presently see on what it rests. 
In the communication read before the Boston Natural History 
Society, besides a brief account of the letter just mentioned, we 
find introduced some comparisons between certain pretended phe- 
nomena which are said to take place in the earlier age of the egg 
and the merely conjectural phenomena of the nebular hypothesis. 
Without further prefatory remarks, I proceed directly to take 
up one by one the facts, the theory, and the speculations. 
I. The primitive egg has been made the subject of much re- 
search by Prof. Agassiz, especially in the department of Mollusca. 
Ascending even beyond the first existence of the egg, he has 
shown us the ovary itself in the process of development. This is 
composed of sacks or pouches varying in form and size, in which 
the eggs are formed. The sacks are filled with an homogeneous 
and transparent liquid. Soon this liquid becomes granular, that 
* Second Series, vol. vi, No. 21, (May, 1849,) p. 395. 
f See Journal of that Society, vol. iii, p. 85. 2 
On the so-called Biogen Liquid. 
is, consists of cells, and the cells becoming more and more nu- 
merous, give birth to a little opaque sphere, which is the vitellus. 
The germinative vesicle and the germinative spot have appeared 
during the formation of the yolk, and sometimes even prior to 
this period; but at the moment when the phase of division com- 
mences, both the spot and the vesicle generally disappear, and in 
the interior of each of the spheres produced by the division, is 
seen a clear space. 
A Resume of these observations has been published.* Since 
then, Mr. Desor has observed analogous phases in other animals. 
He published them, as he had a right to do, but he should have at 
least declared at the outset, that he was doing nothing more than 
repeating the observations which another had made before him. 
II. When an egg has reached that point of its history which 
is called its maturity, it is distinguished by the following charac- 
ters :—a spherical mass, more or less opaque, which is the yolk; 
in the center of this is found a much smaller sphere, the germina- 
tive vesicle, containing another substance, usually transparent; 
then in the interior of this last, a sphere or spheres still smaller, 
the germinative spot or spots. 
The epoch of the appearance of the germinative spot varies as 
it would seem within very considerable limits. This is not the 
place to discuss this question. Let it be observed, however, that 
they exist in every egg when it is mature, and that they disappear 
from every egg when it enters upon the period of division. 
But among the Nemertes a curious phenomenon is observed. 
Generally as we have just said, the vesicle and spot disappear be- 
fore the division of the yolk, or, at least, at the moment when it 
divides in halves. The secondary spheres resulting from the sub- 
divisions of the vitelline mass, have then, each one in its interior, 
a clear space. The question has been raised, what part the ger- 
minative vesicle plays in the history of the eggs? Is the division 
the consequence of its disappearance? in other words, is its con- 
tent necessary to effect the division. The germinative vesicle 
has been considered as containing the primitive elements of the 
new being, or an element indispensable to its formation. Now 
here, among the Nemertes we meet with a case where the yolk 
is already divided into four parts, while the germinative vesicle 
still exists. The division of the yolk, then, can take place with- 
out the previous bursting of the germinative vesicle. 
This fact is set forth and illustrated fully in the Lectures on 
Comparative Embryology,! and what appears strange to us, is, 
that Mr. D. now takes for his own, an observation to which he 
strongly objected when it was first communicated to him. Hav- 
* Lectures on Comparative Embryology, by Louis Agassiz. Boston. January, 1849. 
f Pages '70,71. On the so-called Biogen Liquid. 
3 
ing made his observations upon a species different from that in 
which the fact was originally observed, there was, it seems to me, 
sufficient merit in pointing it out in another species, without 
claiming for himself the absolute priority. 
III. In 1840, Mr. Martin Barry and Prof. Valentin, simultaneous- 
ly observed, the one in England in the egg of the Rabbit; the other 
upon the shores of the Mediterranean, in the egg of a sea Urchin, 
(jEchinus lividus,) that the germinative spot is not so simple as 
had been previously supposed. The observations of Mr. Barry 
were published during the same year those of Prof. Valentin, 
written in 1840, did not appear till 1842, and at this time he was 
still unacquainted with those of the English micrographer, for he 
would not have failed to mention observations so curious and a 
coincidence so remarkable. Prof. Valentin merely says that a 
round opaque body is often discerned in the center of the germi- 
native spot.f In 1841, Van BenedenJ observed a granule in the 
germinative spot of the Hydractinia rosea, and in 1844,<§> when 
reconsidering the same species, he detected an opaque corpuscle 
within the germinative spot. This fact I have verified in 1848, 
in the case of the common sea Urchin (or sea egg) of Massachu- 
setts Bay. 
More recently Mr. D. says, that he has observed in a worm 
(Sigalion), and a sea anemone {Actinia), that the germinative 
spot contains a clear transparent vesicle. Comparing then this 
clear vesicle with the opaque nucleus observed by Prof. Valentin, 
he calls it Vesicula Valentini. 
We honor the homage rendered to Prof. Valentin :—but Mr. D. 
has failed to explain how it happens that a transparent vesicle in 
the worms and sea anemone, is the same thing with the opaque 
nucleus of the sea Urchins; and moreover he ought not to have 
overlooked two points of its history, those which belong to Mr. 
Barry and Van Beneden. By examining more closely, and study- 
ing more intimately the contents of the germinative vesicle and 
of the germinative spot, he might have satisfied himself that the 
presence of a clear vesicle, or of an opaque nucleus, indicates only 
two states of one and the same phenomenon, since they are ob- 
served alternately in the same species. This is the case with the 
eggs of Ascidiae, of Medusae, of Echini, and probably the eggs of 
many others. 
By merely reading the paper of Mr. Barry, he might have been 
convinced that this observer had seen much deeper than any of 
* Researches in Embryology: Third Series, 
f Anatomie du genre Echinus, p. 105, PL viii, fig. 167. 
\ Bulletin de 1’Academie de Bruxelles. 
§ Recherches sur l’embryogenie des Tubulaires.—Mem. Acad. Brux., vol. xvii, p. 62, 
PI. vi, fig. 6. 4 
On the so-called Biogen Liquid. 
his predecessors. Mr. Barry has pointed out a cellular content in 
the germinative vesicle, a thing then new to science; he believes 
this substance to be produced by changes which take place in the 
germinative spot. I do not enter into more full details upon the 
researches of Mr. Barry, for in that case I should be obliged to 
make some objections of secondary importance, which is not here 
my object. I had only to point out a fact, to correct an oversight. 
1 now return to my subject. 
IY. The researches of Mr. D. upon the development of the eggs 
of xlscidiae, have led him to imagine a theory. This theory rests 
upon a false fact. According to this theory, the primitive state 
of the egg is a little sphere containing a transparent homogeneous 
liquid, in the midst of which sphere, may be already seen the 
outline of the germinative vesicle and spot. By degrees this 
liquid becomes turbid, and the germinative vesicle appears sur- 
rounded by a slight cloud which increases in extent until it fills 
the sphere of the egg. Then finally there is a retreat of the mat- 
ter from the circumference towards the centre of the egg where 
it is condensed and forms the yolk. A free space remains between 
this last and the external membrane. This space is filled by a 
liquid; this liquid is the Biogen. 
Having examined during many weeks and continuously each 
day the eggs of the same Ascidia which was the subject of his 
observation, I have never witnessed this phenomenon. And yet 
I examined them in individuals of very different sizes, and in 
most diverse conditions, taking care always that the egg should 
remain in its natural state; never, I repeat it, did I see this phe- 
nomenon of gradual condensation and of the retreat of the vitel- 
lus. Having tried all the good methods of which we can avail 
ourselves in the use of the microscope, the idea occurred to me 
to compress strongly a fragment of ovary. What was my surprise, 
at seeing living copies of the figures published upon this subject. 
It could even have been easy to make a more complete series 
of them. The eggs were no longer in their natural state; they 
were pressed down or crushed, their natural state destroyed, 
and this was the foundation upon which was built the theory 
of Biogen liquid, which was to apply to the whole animal king- 
dom.* 
What then is the liquid, and what part does it play in the his- 
tory of the egg? This liquid is albumen, the albumen which is 
formed in the ovary, and to judge rightly of the part which it 
takes in the formation of the egg, some general considerations 
upon the primitive state of eggs are here necessary. 
* If the Biogen is so general, I would ask why it was not shown in the Sigalion 
and the Sabella of which Mr. Desor also speaks ? On the so-called Biogen Liquid. 
5 
Prof. Agassiz* has already reminded us that the point of depart- 
ure of the egg is the same as that of the cells of the organic tis- 
sues. There is a period when the ovule is only a minute cell. 
More recent observations confirm these first results. To know 
the origin of the egg, we must then ascend to the origin of cells. 
There are primordial cells, and derived cells. The experiments 
of Dr. Ascherson,f have taught us that primordial cells are formed 
of two substances; of an oily substance and of albumen. Cells 
perfectly like primordial orgauic cells can be made artificially by 
bringing an oily liquid into contact with albumen, although the 
albumen and the oil or oily matter show a perfect continuity of 
substance when we examine them separately. But bring them 
in contact, and cells are formed immediately. Every physiologist 
can repeat these experiments, and ought to do it. 
Primordial cells once formed in the manner above indicated, 
another phenomenon presents itself. They become nucleated, 
and these nuclei enlarging, give birth to derived cells. 
Thus derived cells are multiplied by the growth of the nuclei, 
according to the researches of Mr. Martin Barryof Prof. Agas- 
siz and my own, and whenever the third generation appears, the 
parent cell bursts and allows its contents to escape; it is in this 
way that they increase in number. 
Now the only difference there is between the cells of the tis- 
sues and eggs, is that in these last the parent cell never bursts,§ 
the primordial cell preserves within itself all the subsequent gen- 
erations of derived cells; which by their accumulation, form the 
substance out of which the new individual is produced. 
Applying now this knowledge in a more special manner to the 
development of eggs, we can reply to the question asked above, 
viz., what part does the albumen play? 
At a determinate epoch, for each species, the ovarian sacks are 
filled with primordial cells. It would be premature to raise the 
question whether they are formed in the ovary itself, or are 
brought there already formed. Let us take them, as they exist 
in the ovary. There under the influence of the organism, they 
pass through that course of development which we have pointed 
out as proper to cells destined to become eggs. They contain at 
first oil. By endosmosis albumen passes through the envelop or 
membrane, and coming in contact with the oil, cells are formed, 
the constituent cells of the vitellus (the granules of the yolk). 
* Lectures on Comparative Embryology, 1849, p. 81. 
f Ueber den physiologischen Niitzen der Fettstoffe und iiber eine neue auf deren 
mitwirkung begriandete und durch mehrere neue Thatsachen unterstiitzte Theorie 
der Zellenbildung.—In Muller’s Archiv. fur Anatomie Physiologie, (fee. 1840, p. 44. 
—Comptes Rendus de l’lnstitut, vol. vii, 1838, p. 837. (Sur I'usage physiologique des 
corps gras.) 
1 Researches in Embryology: Third Series. 
§ I mean, at least, as long as the new individual is not ready to escape out of 
the egg. 6 
On the so-called Biogen Liquid. 
When the oil is exhausted, no more cells are formed. The mass 
of the vitellus then increases, after the ordinary method of mul- 
tiplication by the growth of nuclei. The albumen itself contin- 
ues to penetrate through the membrane of the cell, which has 
now become an egg. It remains under the form of albumen, and 
surrounds the vitelline globe with a concentric zone more or less 
thick which increases as the egg grows larger. The intermedi- 
ate space between the yolk and the external envelop (chorion) 
being increased, one would be tempted to acknowledge a with- 
drawing of the vitellus from the circumference towards the cen- 
tre, if it were not known that all parts of the egg enlarge in the 
same proportions. Besides, a yolk which retreats, which is con- 
densed, ought to occupy a less space, while the contrary is the 
fact, even as shown by the drawings made by Mr. Desor himself. 
The conclusion is doubtless, already anticipated, that the pre- 
tended biogen liquid is found to be nothing more than an accu- 
mulation of albumen, the albumen formed in the ovary. An em- 
bryologist would have known that the yolk of the egg of all an- 
imals is composed of albumen and of an oily substance, and that 
no one has ever supposed the first of these two substances to be 
formed in the oviduct. When the albumen deposited in the ovi- 
duct is spoken of, it is the white which surrounds the yolk of the 
egg of certain animals that is referred to, and it is altogether gra- 
tuitous to attribute to embryologists doubts on this subject. I 
think Mr. Desor is the only person who has ever confounded the 
albumen of the vitellus, with the albumen which surrounds the 
essential parts of the eggs common to all animals. 
When mature eggs are to be referred to a uniform type, it is 
necessary to distinguish between the essential parts (the vitellus 
or yolk, the germinative vesicle and the germinative spot), and 
the accessory and protective parts (the external albumen or white, 
the shell-membrane and the shell itself). The former are identi- 
cal throughout the animal kingdom, they are never wanting ; 
they are therefore necessary. The latter are not absolutely neces- 
sary, and as a proof of this, they are modified according to cir- 
cumstances, and, in an infinite number of cases, are entirely 
wanting. 
Starting now from the structure of the egg and knowing it to 
be identical in its constituent elements throughout the whole ani- 
mal kingdom, the doctrine of its crystallization from a mother- 
liquid refutes itself. The idea that the vitellus is precipitated, or 
is crystallized, is indeed very strange. Is not this the distinction 
which we make between the inorganic kingdom and the organic 
kingdom, that the former is crystallized, while the latter is or- 
ganized. 
And then as to the physical characters of this biogen liquid, 
and the method of distinguishing it from albumen, not a word is 
said. All that has been done is the substitution of a name, the On the so-called Biogen Liquid. 
7 
thing newly named is hidden from the eyes of physiologists. To 
explain the formation of eggs in the animal kingdom, Mr. D. 
thus finds himself obliged to procure the intervention of a liquid 
of which he knows nothing,—a liquid which would make the 
function of the ovary of secondary importance,—a liquid which 
would substitute itself for the vital action of the organism, an ac- 
tion which physiology explains,—in fine, an occult liquid, which 
sound philosophy disowns. 
To oppose such a liquid to the vital action of the organism in 
the procreation of the substance, from which new individuals 
arise, is to go out of the domain of science. Mr. D. moreover 
has found that his biogen liquid runs through various modifi- 
cations. This liquid then has no permanent character, it is under 
the influence of something beyond it, which produces it in its turn. 
Anatomy and physiology are our guides in our embryological 
researches ;—one confirms the other. Remaining within these 
limits, it was not necessary to go beyond the bounds of sound phi- 
losophy, and to fancy a theory which rests upon nothing, which 
teaches nothing new, which explains nothing, and which stands 
apart, isolated from physiology. 
Thus the theory of biogen, applied to the egg of Ascidia, is not 
even probable; applied to the animal kingdom it is absurd. 
V. § 1. Prepossessed by the false notion that the vitellus is 
formed by condensation, Mr. D. compares the formation of eggs to 
that of the celestial bodies, according to the nebular hypothesis. 
But in order that a comparison of one phenomenon with some 
other phenomenon may be established, it is necessary that the one 
with which the comparison is made, should be perfectly demon- 
strated,—it must be a law or a principle. 
Now the author forgets that the question of the condensation 
of the heavenly bodies according to the nebular hypothesis, is 
one of the most controverted questions. The fact is that we 
know nothing positively respecting the origin of the stars. Has 
the matter of which they are composed, been diffused through- 
out space under the form of what has been called nebulas, and 
has it been gradually condensed around a nucleus to acquire its 
sphericity under the power of universal attraction, and to assume 
then a given movement and a determined direction ? 
There is no astronomer who can answer this question in the 
affirmative. From the study of our globe we arrive at the idea 
that it has had a beginning, and that it was originally in a fluid 
state. Beyond this, all is conjecture. Reasoning from the earth 
to the stars, we acknowledge, for all, a beginning of which we 
are ignorant. 
It is then a false generalization to compare the phenomena of ovu- 
lation with the theory of the condensation of the sidereal bodies. 8 
On the so-called Biogen Liquid. 
But let it be for a moment granted that the stars have been 
formed by the condensation of matter at first diffused. Where is 
the analogy between what ought then to take place, and what 
we witness in the formation of the egg ? 
The point of departure of organized beings is a sphere—the 
sphere is the figure of the celestial bodies; this is the whole of the 
analogy! In that sphere which constitutes the egg, two liquids 
are brought in contact and having an affinity for each other, 
they combine and form the vitellus which, from the first, is dis- 
tributed equally throughout the whole sphere, less dense, it is 
true, at the beginning; but never showing the least tendency to 
centripetal motion, the least disposition to be precipitated around 
the germinative vesicle. There is never any retreat of the vitel- 
lus from the periphery towards the centre; there is no gravitation ; 
there is a molecular attraction in the interior of a sphere, there 
are two liquids which are associated together, and not one liquid 
creating another out of itself. 
Thus then should the theory of the condensation of the heav- 
enly bodies be true, that of the eggs arising from biogen would 
not even be its analogue. Where is the biogen of the stars? No 
astronomer has had the hardihood to imagine a mother liquid, a 
gas, or any substance whatever preexisting in space to create mat- 
ter, and to disappear after having undergone various modifications. 
$ 2. But Mr. D. stops not here. After having found the great 
la w of attraction at the bottom of the formation of organic bod- 
ies, he comes to the question of movement. “ As soon,” he says, 
“as the egg enters upon its organic life, it begins to revolve.” 
There are, indeed, a few invertebrated animals in which the em- 
bryo is subjected to a rotatory movement within the envelop of 
the egg. When one witnesses this for the first time, his thoughts 
naturally revert to the rotatory movement of the celestial bodies. 
But on looking deeper into the subject, he soon perceives the dif- 
ference. I have described the movements which take place in 
the embryo of a marine Planaria.* I have shown that there is 
nothing regular about them, no subjection to law. The young 
animal itself regulates and controls them. There are vibratory 
ciliae, that is to say, organs of locomotion, and where these do 
not exist, vibratory cells. There is not an external force under 
the dominion of which it is caused to move. 
The egg possesses organic life from the moment when it ap- 
pears under any form whatever, therefore it cannot be said to ac- 
quire it when it begins to move. Besides eggs, as eggs, move not ; 
when they move they are no longer eggs; they are embryos. 
For when movement occurs it does not take place till after the 
division of the yolk ; and after that division, the embryo exists. 
So that in this view also, the comparison is false. 
* Proc. of the Amer. Assoc, for the Adv. of Sciences. Second meeting, held at 
Cambridge, August, 1849. Cambridge, 1850. 8vo, p. 400.