L] BLASTODERMIC VESICLE. 315 



I)Out 0'09 mm. the size of the ovum at the close 

 igmentation to about 0'28 in diameter. It is en- 

 osed by the zona radiata and the albuminous layer 



Fig. 96. 



bABBiT's Ovum between 70 90 Hours after Impregnation. 

 (After E. van Beneden.) 



Iv. cavity of blastodermic vesicle (yolk-sac) ; ep. outer layer ; 

 hi/, inner mass ; Zp. albuminous envelope. 



Iiround it. The blastodermic vesicle continues to 



Imlarge rapidly, and during the process the inner mass 



mdergoes important changes. It spreads out on the 



mer side of the outer layer and at the same time loses 



Its lens-like form and becomes flattened. The central 



