Cuar. I. GROWTH OF THE OVARIAN EGG. 479 
spirits and kept for reference, as may be seen in my embryological collection. 
I mention these trifling circumstances, only the more fully to satisfy the reader 
that these investigations were made upon parts of the egg duly isolated for a satis- 
factory microscopic examination. 
SPHCOTION V'- 
THE GROWTH OF THE OVARIAN EGG, AS A WHOLE. 
Thus far we have described in detail the origin, the development, and the 
maturation of the several constituents of the ovarian egg of Testudinata. Now, 
in order to arrive at a full and comprehensive understanding of the general rela- 
tions which exist between the several elements of this complicated structure, among 
each other as well as with reference to the whole organism of the egg, it is neces- 
sary to combine, in one view, all the details which have been before presented as 
separate and independent features. We have, indeed, up to this time, considered 
the different parts of the egg as constituting separate organs, as it were, grow- 
ing each one independently, as regards the peculiar plastic force operating therein. 
We have shown that each of these parts is distinguishable from every other by 
dissimilar characters; and yet they are all connected by a superior power, which 
holds them im obedience to the one great law of correlation controlling the growth 
of every organized being. 
In a former section’ we have followed the growth of the egg as a whole, 
up to that period when the homogenity of its contents begins to be disturbed 
by the introduction of the yolk cells in the form of dark granules. At this stage 
the Purkinjean vesicle is a very clear globule, usually situated in that part of 
the egg which is most distal from the side where the granules appear (Pl. 8, 
fig. 4, 5, 6, 8, 9, 10, etc.) The next step brings an encroachment of the gran- 
ular region upon that which surrounds the Purkinjean vesicle, simultaneously with 
the appearance of the Wagnerian vesicles in the latter (Pl. 8, fig. 13a, 15, 17, 17a, 
18a, 19); thus exhibiting no inconsiderable change in the internal life of the egg. 
In the succeeding stage, the yolk granules are replaced by mesoblasted cells, (Pl. 
8, fig. 22, a-d, 25, 25a-23d, 24, 24a, 25, a-e, ete.) accompanied by an enormous 
increase of the Purkinjean vesicle (Pl. 8, fig. 22, e, 24b); from this time also 
the differentiation in the size of the yolk cells becomes conspicuous, those around 
1 See Sect. 1, p. 451-457. 
