Text-fig. 3. 



Surface view froui the animal pole of a later stage ; the apical 

 ectoderm is now formed from 8 cells of the first quartette 

 of micromeres, 16 of the second, and 6 of the third ; 2a^\ 

 2b'\ 2c'-\ and 2c^'-' are the tip cells of the apical cross. 



Text-fig. 4. 



Egg seen from the vegetative pole at a stage corresponding to 

 Text-fig. 2. The mesoteloblast M is already formed by the 

 division of D. 



