" the Ovum. 755 
I the cavity of the embry- 
is a yolk-sac, in the walls 
-Hcapt. 
qualities, since it is thence taken up i 
onic vesicle, which eventually functions as 
of which embryonic blood-vessels ramify.' 
The inner mass (Fig. 11, z'.w.) does not at first grow much, 
and retains its rounded form, becoming, at least in the mole, 
nearly globular. (Fig. 12, A.) The inner mass subsequently 
flattens out, becoming len'^-shaind, thinn. !, and of larger area. 
(Fig. 12, B.) It continik-^ and separates into 
thin epithelial r 
a lens-shaped w. 
• three layers \\x ; 
and have been 
these three lavcrs wi 
thin 
/er of 
Rauber, however, showed that both the 
