12 



the cpllc- is iTore irropulrr r.rd ovhtif: to the- cracity of the 

 egg it is difficult to follov; with accuracy the derccrt of 

 the cells. Frgure IT. rhcv/c a ]atcr stare in v.'hich the ar- 

 ranperert of the cells is mere regular than is frecuently 

 TTiet with ir eggs of the sane age. 



As strtod before, the divisiors follov/ each other at 

 short intervals. \Vith:n tv;o hours after the eggs vrere laid 

 they had undergone the ^rocess of laturatior a-d fer- 

 tilization, a-d had "passed beyc^d the sixty-four celled 

 stage, ;he cells continue to divide with the sa-e raridity, 

 while within the^ ihe cleavage cavity is alsr gradually en- 

 larging. Finare 1." shows a stage in v.'hich the cells are 

 more or less definitely nlaced around the segmentrtion cavity. 

 The blastoreres fi^^aHy beccT^e very numerous ard srali, 

 ard arrange the-selves around the blastoccele in a single 

 celled layer for'^ing a true blastula. 



BI.ASTULA. 



'he blastula ir oval in share, and is but slightly 



