SPERM ATOdEN ESI S 



287 



of the lumen. Thv nucleus is oxal and somewhat elouf^ated, 

 Sertoli cells occur at ((uite rciijular intei'xals around the lumen of 

 the tuhule and establish close relationshi]) with the more numerous 

 and smaller developinij; s])ermato(jenic cells. 



'rmatagonia 



SecoTidary spermatocyte 



Spcrmatazoa 



a, h, c = Stages 



in sperniiogeyiesis 



Fig. 147. — Diagram of a section through a seminiferous tubule, showing formation of 

 spermatozoa from spermatogonia! cells. 



Spermatogenic Cells. — Beginning at the basement membrane, and 

 extending in toward the lumen, spermatogenic cells form a stratified 

 epithelial tissue several layers deep, interrupted at regular intervals 

 by Sertoli cells. We have already studied the growth of stratified 

 squamous epithelium, and the acti\ity of these spermatogenic cells 

 presents something of the same sort, l)ut of a more highly specialized 

 nature. ^Yhen acti\ity begins wliich will ultimately lead to the 

 formation of sperm, a series of mitotic divisions take place, during 

 which daughter cells of the dividing basal cells are constantlv ])ushed 



