126 



T. H. MORGAN. 



DESCRIPTIVE. 



Rana palustris. Since I now have a more complete series 

 of stages of the eggs of this species, and since I have elsewhere 

 especially considered this form, it may be dealt with first. 



9 10 



Kics. 5-10. Later segmentation stages and gastrula stage (Fig. lo) of Kana 

 palustris. 



Fig. I is a vertical section of an eight-celled stage. The seg- 

 mentation cavity is present and is bounded above by the upper 

 four cells (of which two are seen in the section), and at the sides 



