378 



THE MALE REPRODUCTIVE ORGANS 



Mitotic division of the cells of the second generation or inner 

 row of spermatocytes results in the formation of two spermatids. 

 Hence each spermatocyte of the first order, producing two sper- 

 matocytes of the second generation, ultimately forms four sper- 

 matids, each of which is finally transformed into a spermatozoon. 

 A peculiar fact in connection with this process is that in one of 

 the mitotic divisions of the spermatocyte the chromosomes fail to 

 divide in the ordinary manner, thus producing one-half the 

 usual number of daughter chromosomes. This results in a reduc- 

 tion of the chromosomes during the spermatocyte stage to one- 

 half the number elsewhere characteristic of the species. This 

 " reduction " in the male germ, which is paralleled in the female 

 during the development of the ovum, is of 

 great importance in its relation to the proc- 

 esses of fertilization and maturation of the 

 germ cell. 



The spermatids formed by the division of 

 the second generation of spermatocytes, are 



FIG. 307. THREE PHASES OF SPERMATOGENESIS IN THE SEMINIFEROUS TUBULES OF THE 



RAT'S TESTICLE. 



A, the formation of spermatosomes ; 5, discharge of the spermatosomes ; (7, formation 

 of the spermatoblast ; /, fat droplets, blackened by the use of a fixative which contained 

 osmium tetroxid ; fc, fat and stainable granules ; m, basement membrane ; s, spermato- 

 somes ; sc, spermatocytes ; sg, spermatogonia, in mitosis at sg'; sp, spermatids ; St, cells 

 ofSertoli. Saffranin. x 540. (After Kolliker.) 



