THE DUCTUS DEFERENS 



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divisions or stages, form ultimately the male reproductive cells, or sperm 

 cells. 



The important stages in order are: archispermiocyte, spermatogonia, 

 primary and secondary spermatocytes, spermatids, and spermatozoa. The 

 spermatogonia stage is the stage of rapid multiplication; the spermatocyte, 

 that of maturation, comparable to the maturation stage of the ovum. 



The spermatozoa, or sperm cells, are the essential male reproductive cells. 

 Each mature spermatozoon consists of a minute oval head, a middle piece, and 



SfC.l 



\ 



spg.r 



FIG. 488. Later Stages in Spermatogenesis of the Bull, spg.r, Reserve spermato- 

 gonium; spg, spermatogonium; spc.g, spermatocyte in late synapsis stage; spc.i, spermacyte 

 in stage just preceding the maturation divisions; spd, spermatids in advanced stage of 

 histogenesis, with heads deeply embedded in Sertoli cell. Highly magnified. (After 

 Schoenfeld.) 



a tail. The head consists almost entirely of the cell nucleus, while the mid- 

 dle piece and tail are cytoplasmic structures. The head is 4/z by 2.5^. 

 The middle piece and tail are about 50 to 6o/z long. The tail is essentially 

 a cilium, and exhibits the power of flagellate movement. 



The Ductus Deferens. This is the single duct proceeding from each 

 testicle to join its fellow at the base of the bladder. Each has an ampulla or 



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