THE REl'RCMJUCTIVE SYSTEM 



343 



(2) Spermatocyte s (Figs. 235 and 236, sc). — These are larger spher- 

 ical cells with abundant cytoplasm and large vesicular nuclei showing 

 various stages of mitosis. They form from two to four layers to the 

 inner side of the spermatogones, and are 

 sometimes differentiated into spermat- 

 ocytes of the first order and spermato- 

 cytes of the second order. By mitotic 

 division of the innermost spermatocytes 

 are formed the spermatids. 



(3) The sperj iialids (Figs. 235 and 236, 

 st) are small round cells which line the 





Fig. 237. , 



Fig. 237. — Passage of Convoluted Part of Seminiferous Tubules into Straight Tu- 

 bules and of these into the Rete Testis (Milhalkowicz.) a, Convoluted part of tubule; 

 b, fibrous stroma continued from the mediastinum testis; c, rete testis. 



Fig. 238. — Spermatoblast with some Adjacent Sperm Cells, from Testis of Sparrow. 

 (From Kolliker, after Etzold.) M, Basement membrane; s, nucleus of SertoH cell; sp, 

 spermatogones; sc, spermatocyte; sti and st-2, spermatids lying along the surface of 

 the Sertoli cell, s' and sh; at 5/3 are seen the nearly mature spermatozoa; /, tuft-like 

 arrangement of bodies of spermatids around free end of Sertoli cell, with two mature 

 spermatozoa. 



lumen of the seminiferous tubule. They are the direct progenitors of 

 the spermatozo a. (For details of spermatogenesis see page 350.) 



In the actively secreting testicle spermatozoa are frequently found 

 either free in the lumen of the tubule or with their heads among the 

 superficial cells and their tails extending out into the lumen (Figs. 

 235, sf^ and 238). There are also found in the lumen many small 



