ACCOUNT OF THE GEKM-CELL CY( LE 45 



Fig. 10. — Diagrams showing the (.^sential facts of ri'tluction in the 

 male. The somatic number of chromosomes is supposeil to bo four. 

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

 of chromosomes. C, primary spermatocyte i^rcparing 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 .><ingl(' chromnsonies and 

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

 (After Wilson.) 



