MATURATION. 



23 



spin 





. "' : "$ft'- 







spm 





spm 



C D 



Fig. 15. — From sections of seminiferous tubules of Rat, showing successive stages in spermato- 

 genesis. Lenhossek. 



A, Typical section showing clumps of spermatozoa (spz) with their heads embedded in Sertoli cells; 



several layers of spermatids (spm); layer of spermatocytes (spc) with nuclei preparing for 

 division; layer of spermatogonia (spg) next basement membrane. 



B, Section showing beginning of transformation of spermatids (spm) into spermatozoa; spermato- 



cytes (spc) with larger cell bodies and spiremes in nuclei. 



C, Section showing large spermatocytes (spc) in process of division; spermatogonia (spg) pre- 



paring for division to form new spermatocytes. Spermatids of preceding stage (B) are repre- 

 sented here by spermatozoa (spz). 



D, Section showing further advance. The primary spermatocytes of the preceding stage (C) 



have divided to form secondary spermatocytes and the latter to form the spermatids (spm) 

 represented here. During these divisions the reduction of chromosomes has taken place. 

 The spermatogonia of the preceding stage have divided, one daughter cell from each forming a 

 new spermatocyte (spc), the other still remaining as a spermatogonium (spg). 



