404 On the so-called Biogen Liquid. 
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). 
When the oil is exhausted, no more cells are formed. he 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 1s 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. ia 
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), an 
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. 
