r 



THE GERM-CELLS 



(6) SPERMATOGENESIS. 



The observation of the reducing division in the ovum 

 suggested to biologists to look for a similar process in the 

 male germ-cell. This process was actually found to occur, 



B 



a , 



FIG. 30. SPERMATOGENESIS AND MATURATION OF THE OVUM COM- 

 PARED. (After Hertwig, Weismann, and Delage.) 



A , Spermatogenesis. a^, the primitive sperm-cell ; 2 > the mother 



sperm-cell ; a 3 , two sperm-cells ; a 4 , four sperm-cells. 



B, Maturation of Ovum. b 1} the primitive ovum ; b 2 , the mother 



egg-cell ; 6 3; ovum and first polar body (pb-j) ; & 4 , ovum with 

 second polar body (pb^, and division of first polar body into 

 two. 



but it is here slightly different from the ovum ; for while 

 the ovum rids itself of half its chromosomes during its 

 maturation, the halving of the chromosomes in the sperm- 



6 



