464 EMBRYOLOGY OF THE TURTLE. Part III. 
in the aspect of the yolk, at the period of initiative cell genesis, is the hya- 
lescence of the coarser granules,’ and a rounding of their contours (Pl. 8, fig. 20a). 
At this time the egg is about one sixteenth of an inch in its mean diameter. 
> ») 
(Pl. 8, fig. 20.) 
sented, although in a manner already familiar, namely, in the drop-like form, yet 
The recurrence of a superabundance of albumen is here pre- 
with an essentially different anticipation. The function initiated at this period 
would lead us to suspect, nay, almost to demand, that something more than 
an adventitious globular concentration of amorphous substance must be silently 
working before us. And so easily is this suspicion put at rest, in a positive 
manner, that we very soon forget that there was once a moment of hesitation 
respecting the nature of this development. It has already been stated, that 
there is a difference in the progressive development of the smaller ovarian eggs 
and those which afterwards appear in separate sets, corresponding to the number 
of eggs which different species of Turtles annually lay. The eggs which we 
are now considermg belong to the earliest set of somewhat larger eggs, which 
appear in definite numbers, and may be distinguished from the innumerable mass 
of smaller eggs scattered through the whole ovary” I have further observed, that 
the youngest Chrysemys picta found in copulation had no larger eggs than these. 
It is, therefore, plausible to suppose that the changes which now follow, in the 
development of the yolk, are the natural consequence of a first connection of 
the sexes, which is repeated twice annually, for four successive years, before the 
egos are laid; as will be ‘shown more fully in another section. 
But, let us return to the eggs in which the formation of the yolk cells is just 
beginning. The instant that water is allowed to act upon a portion of the yolk, 
by the following names: ectoblast is applied to the 
outer envelope; mesoblast to the so-called nucleus ; 
entoblast to the so-called nucleolus; and, when this 
contains a still smaller body, this is called entostho- 
blast. In the nomenclature of the egg, similar objec- 
tions may be raised against the use of germinal or 
germinative vesicle and dot, as neither of these parts 
has the slightest reference to the formation of the 
germ. We shall therefore designate them, henceforth, 
as some embryologists do, by the names of the Pur- 
kinjean and Wagnerian vesicles. Applying our no- 
menclature to a comparison of the egg with the cell, 
the yolk membrane is to be considered as an ectoblast, 
the Purkinjean vesicle as a mesoblast, the Wagnerian 
vesicle as an entoblast, and the Valentinian vesicle as 
an entosthoblast. 
1 By the “hyalescence of the coarser granules,” 
it is not meant that already existing angular, coarse, 
dark granules become hyaline, but that they disap- 
pear now, as they have again and again been changed 
before, and clearer and round bodies take their place ; 
the action of some novel influence, probably the fecun- 
dation, inducing the genesis of new forms. 
2 Comp. p. 460. 
represented on Pl. 9 were observed out of the breed- 
The eggs of intermediate sizes 
ing season. After eggs like that of fig. 10 have been 
laid, those of the second set (fig. 8) soon grow to the 
size of fig. 9; those of fig. 5 and 6 to that of fig. 7; 
those of fig. 1, 2, 3 to that of fig 4; and a new 
set, like the eggs of Pl. 8, fig. 20 and 21, start in ad- 
vance of the smallest ovarian eggs, which cannot yet 
be distinguished in sets. 
