482 EMBRYOLOGY OF THE TURTLE. Part III. 
through the oviduct; nay, even that the ovarian ege is essentially the animal 
itself, developed to a certain degree of complication, which, if freed from the 
parent and cast into the world without passing through the last fecundation, finds 
itself in an unnatural element, and dies; but, if subjected to this vivifymg impulse, 
is sustained for a much longer period. The antagonism observed between the ele- 
ments of the egg, durmg its ovarian growth, is carried out further, during the 
whole life of the growing animal. The region at first occupied by the Purkinjean 
vesicle corresponds afterwards to the cerebro-spinal side of the embryo, whilst the 
vitellme region marks the nutritive or intestinal sphere of the new being. 
However much the nature of the immature egg, as described above, may seem 
to identify it with the budding progeny of some animals, we are not prepared 
to admit a parallelism between the two; on the contrary, knowmg the mode of 
origin of the former and the totally diverse derivation of the latter, we cannot 
see any common ground upon which the two processes could be identified. 
We hope, in another volume, probably the next, fully to discuss this subject, 
in connection with another type of animals, the Hydroid Medusx, in which these 
two modes of procreation obtain in the utmost diversity of combinations. 
SHCTION, Vi: 
THE GRAAFIAN FOLLICLE, AND THE MEMBRANES OF THE EGG. 
The Stroma. 
ment of this layer, and can only offer a few suggestions, which may lead to fur- 
We have very little to say in regard to the mode of develop- 
ther investigations hereafter. An ege hardly yet visible to the naked eye is 
covered by very faint traces of a semi-fibrous, semi-cellular, exceedingly transpar- 
the genesis of the embryo. 
This mode of origin float. True enough, the region about this vesicle ex- 
alone, we maintain, is sufficient to show that the very 
foundation upon which its importance is laid cannot 
be tenable, in this light. The Purkinjean vesicle, 
therefore, loses all its advocated claims to preponder- 
ance over the rest of the egg constituents; to say no- 
thing of the fact that it takes no part in the building 
up of the blastoderm, excepting that its discharged 
contents may become absorbed in the endosmotic and 
exosmotic interchanges of substances between the oily 
yolk cells, and the albuminous matter in which they 
hibits a specialized nature; it is there that the em- 
bryo first develops certain of its characteristics, pre- 
vious to its further extension; but it does not follow, 
that, because the Purkinjean vesicle is situated there- 
about, it is the basis of this evolution, or in any way 
causatively connected with it. On the contrary, its 
presence is itself rather the result of certain ten- 
dencies, for instance, the concentration of albumen in 
that direction ; and its disappearance also is the con- 
sequence of the consummation of these tendencies. 
