GERM-CELL CYCLE IN ANIMALS 



of chromosomes and the amount of chromatin in 

 the germ cells. Typically, both male and female 

 germ cells divide twice during the process of matura- 



PRIMORDIAL 

 GERM-CELL 



MULTIPLICATION 

 PERIOD 



SECONDARY 

 SPERMATOCYTES 



SPERMATOZOA 



MATURATION 

 PERIOD 



PRIMORDIAL 

 GERM-CELL 



PRIMARY 

 OOCYTE 



SECONDARY 

 OOCYTE8 



(OVARIAN EGG 

 AND POLAR. BODY; 



MATURE EGG 



AND 



POLAR BODIES 



MULTIPLICATION 



PERIOD 



MATURATION 

 PERIOD 



FIG. 9. Diagrams illustrating (above) the stages of spermatogenesis 

 and (below) of oogenesis. The primordial germ cell is represented 

 as possessing four chromosomes. 



