CLEAVAGE AND (JASTKULATION. 



537 



D 



E 



F 



G 



If 



Fig. 279. — Cleavage of Aw-phioxus (after Salenskt). A, egg before cleavage, with 

 the polar bodj ; />'. division into twOj the two cells being still connected by a band 

 i>i protoplasm; < '. tour-celled stage; I), the saint- seen from the pole; I'., eight- 

 celled stage ; /•'. sixteen-celled stage ; 67, stage showing more rapid division at the 

 animal pole : one of the circles of cells is in the act of dividing ; //. the same stage 

 in section ; /, blastula, surface view/ A", blastula, in section. 



