Bibliography. 218 
. is the order of events in the formation of an ovum ; a simple cellule is 
first produced in the substance of the ovary, which has been denomina- 
ted “‘la vesicule germinative,” germinating vesicle, or vesicle of Pur- 
_ kinje; this, after it has acquired a certain size, forms exterior to and 
enclosing itself, a second which is the “ vitelline membrane,” and at 
the same time there is formed in the interior of the germinating vesicle 
a number of granules, which constitute what is called, the ‘tache” or 
“taches germinative,” germinating spot or spots—they being for the 
most part grouped together, so as to form a single granular mass. 
These different parts once formed, increase in size, but in different pro- 
portions. When. first. formed, the vitelline membrane is only large 
enough to enclose the germinating vesicle; but when the vitellus is 
perfectly formed, it is many*times larger. The entire ovum having 
acquired the diameter of § line escapes from the parietes of the ovary 
into the cavity of the abdomen, having previously acquired an envel- 
oping membrane, which corresponds to the shell membrane of the eggs 
of birds. 
The mature ovum, which is susceptible of impregnation, is nearly 
transparent, having a slightly yellowish tinge, resulting from the pres- 
ence of globules of oil in the vitellus, which, in consequence of their 
lightness, occupy its most elevated portions, constituting what is de- 
nominated the oil disk. The vitellus contains no cellules whatever, 
and has a very strong resemblance to albumen. Immediately on be- 
ing immersed in water, the latter penetrates the shell membrane, and 
accumulates between it and the membrane of the vitellus, occupying 
- the place of albumen. in the eggs of birds and reptiles, which has no 
existence in ova of the C. palwa. The vitellus floats and turns freely 
in the watery. fluid. en ee el 
As to the effects of the seminal fluid, the author says but little, al- 
though beyond a doubt indispensable tothe development of the genus. 
The difficulty of appreciating its immediate effect, may be estimated 
from the fact that impregnated and unimpregnated ova manifest, during 
the first day, precisely the same changes; after this period, however, 
the difference is striking ; the ova going on through the successive steps 
of the development of organs, and the other becoming opaque, soon 
passes into a state of putrefaction. 
_ M. Vogt has given detailed descriptions and figures of the evolution 
of the different organs, and the changes which they undergo during em- 
bryonic life 3 not commencing, however, with the first appearance of 
individual organs merely, but going back to the formation of the cel- 
lules, out of which the organs themselves are generated. ‘I'he nervous 
system, skin and muscles, intestinal canal, with its appendages, and the 
sanguiferous and respiratory systems are described in turn, as they 
