162 THE PHYSIOLOGY OF REPRODUCTION 



m.Miibrane. 1 The layer nearest the membrane consists of clear 

 cubical cells, a few of which show evidence of division. These are 

 th- spermatogonia. Certain of the epithelial cells between the 

 apermatogonia are enlarged, and project among the more internal 

 cells in association with developing sperms. These are the cells of 



Fn:. 48. Section through portion of two seminiferous tubules in testis of rat. 



iseinfiit-menibrane ; />, spermatogonium ; r, spermatocyte; </, sper- 

 matozoa in cavity of tubule ; e, interstitial tissue containing vessels. 



>li. ( >u the inside of the spermatogonia are certain larger cells, 

 known as spermatocytes. These are products of division of sper- 

 matogonia, each of which on dividing into two gives rise to a cell 

 like itself, and another cell, which grows larger, passes into the 

 second layer, and becomes a spermatocyte. 



The spermatids, which in some seminiferous tubules lie on the 



1 Curtis, "The Morphology of the Mammalian Seminiferous Tubule," .\ m?r. 

 Jo>n: <>f .\i-'it . vol. xxiv., 1918. 



