ACCOUNT OF THE GERM-CELL CYCLE 45 



Fig. 10. — Diagrams showing the essential facts of reduction in the 

 male. The somatic number of chromosomes is supposed to be four. 

 A, B, division of the spermatogonia, showing the full number (four) 

 of chromosomes. C, primary spermatocyte preparing for division; 

 the chromatin forms two tetrads. D, E, F, first division to form 

 two secondary spermatocytes, each of which receives two dyads. 

 G, H, division of the two secondary spermatocytes to form four 

 spermatids. Each of the latter receives two single chromosomes and 

 a centrosome which passes into the middle piece of the spermatozoon. 

 {After Wilson.) 



