347 



does not ditferentiate from material lying at the upper pole of the 

 egg as is the case in Rana, Bufo, Acris and Amblystoma; 



2) that neither the first nor second cleavage; grove bears a con- 

 stant relation to the median plane of the future embryo. 



Series IL Twenty eggs in early gastrula stages were punctured 

 at points midway between the upper pole of the egg and the dorsal 

 lip of the blastopore. The locality punctured is shown by the cross- 



