264 



WILLIAM B. KIRKHAM. 



has its chromosomes gathered into a single compact mass. It 

 quickly forms a resting nucleus, possessing compact masses of 

 chromatin, and is usually the only polar body seen during the 

 early cleavage stages. In one instance (Fig. 6.) a second polar 

 body was observed which had just been constricted off, and in 

 consequence showed the separate chromosomes, twelve in num- 



FlG. 6. Egg in Fallopian tube showing second polar body. First polar body has 

 disappeared. At left in the egg is seen the sperm nucleus, and above it the separated 

 tail of the spermatozoon ; at right appears the egg nucleus, surrounded by delicate 

 radiating fibers. X 1200. 



ber, and another preparation showed the second polar body form- 

 ing the resting nucleus. 



The mouse egg is thus shown to be no exception to the general 

 rule, that the maturation process in the metazoon egg involves 

 the formation of two polar bodies. 



In closing, I desire to express my gratitude, and great indebt- 

 edness to Professor Wesley R. Coe for his constant oversight 

 and encouragement. 



