CLEAVAGE AND GASTRULATION. 



537 



C 



I) 



B 



Fi;. 'J7H. CltMvuge <>f J /////// /",<-/'.v (after SALENSKY). .4, egg before cleavage, with 

 the polar body ; tt, division into two, the two cells being still connected by a baud 

 .if protoplasm; O, four-celled stage; U, the same seen from the pole; E, eight- 

 celled stage ; F, sixteeu-celled stage ; V, 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/ K, blastula, in section. 



