130 



T. H. MORGAN. 



with'which it is continuous further inwards, projects upwards at 

 the anterior end of the egg into the blastoccel. On the opposite 

 side of the section, the downgrowth is less developed, and the 

 yolk-floor less elevated. 



20 21 



FlGS. 16-21. Segmentation and gastrulation stage (Fig. 21) of Rana sylvatica. 



The general conditions in this species are the same, in all essen- 

 tial respects, as in the last. 



Bufo Icntiginosns. - - The toad, although belonging to another 

 family of the Anura, follows very closely the same method of 

 early development as the frog. In several respects it shows with 

 great clearness some of the early changes that I have described 



