THE MALE ORGANS 345 



heterotype mitosis occurs at the formation of the spermatids, 

 and in the female at the casting off of the second polar 

 body. The spermatozoon and mature ovum therefore 

 contain each of them half the amount of chromatin. At 

 the fusion of the nuclei in fertihsation the normal amount 

 of chromatin is restored. The reduction of chromatin 

 is therefore a device for the prevention of the doubhng of 

 the chromosomes at each new generation. 



Fig. 62. — Plan of arrangement of tubules and ducts of testicle (from 

 Schafer's Essentials of Histology, after Quain) : a, seminiferous 

 tubules ; 6, straight tubules ; c, rete testis ; d, vasa efierentia ; 

 e, f, g, epididymis ; h, vas deferens ; t, tunica albuginea with 

 trabecular. 



THE MALE ORGANS OF REPRODUCTION 



The Testis and Vas Deferens 



The testis consists of a number of seminiferous tubules 

 grouped into lobules by strands of fibrous tissue. These 

 strands arise from a fibrous mass called the mediastinum 

 testis, which is situated posteriorly and is continuous with 

 the tunica albuginea or sheath which invests the testis. 

 In the connective-tissue between the tubules are cells of 

 epithelioid form — the interstitial cells. The seminiferous 



