The Cellular Basis 



141 



and even photographed, while in the living condition. The peri- 

 pheral layer of protoplasm is yellow and it gathers at the lower 

 pole of the egg, where the sperm enters, forming a yellow cap 



Fig. 45. Successive Stages in the Cleavage of the Egg of a Mollusk 

 (Crcpidula), showing the separatcness of the male and female chromo- 

 somes ($ch, V ch) and of the male and female halves of each nucleus 

 ($N, 9N). 



