724 



AMNIOTA. 



been detected by myself (No. 555) in Mammals. It is not 

 certain to what parts of the testicular tubuli they give rise, but 

 they probably form at any rate the vasa recta and rete vas- 

 culosum. 



In Mammals they also occur in the female, and give rise to 

 cords of tissue in the ovary, which may persist through life. 



The comparison of the tubuli, formed out of these structures, 

 with the Elasmobranch and Amphibian testicular network is 

 justified in that both originate as outgrowths from the primary 

 Malpighian bodies, and thence extend into the testis, and come 

 into connection with the true seminiferous stroma. 



As in the lower types the semen is transported from the 

 testicular network to the Wolffian duct by parts of the glandular 

 tubes of the Wolffian body. In the case of Reptilia the anterior 

 two or three segmental tubes in the region of the testis probably 

 have this function. In the case of Mammalia the vasa efferentia, 

 i.e. the coni vasculosi, appear, according to the usually accepted 

 view, to be of this nature, though Banks and other investigators 

 believe that they are independently developed structures. Further 

 investigations on this point are required. In Birds a connection 

 between the Wolffian body and the testis appears to be estab- 

 lished as in the other types. The Wolffian duct itself becomes, 

 in the males of all Amniota, the vas deferens and the convoluted 

 canal of the epididymis the latter structure (except the head) 

 being entirely derived from the Wolffian duct. 



In the female the Wolffian duct atrophies more or less 

 completely. 



In Snakes (Braun) the posterior part remains as a functioriless canal, 

 commencing at the ovary, and opening into the cloaca. In the Gecko 

 (Braun) it remains as a small canal joining the ureter ; in Blindworms a 

 considerable part of the canal is left, and in Lacerta (Braun) only interrupted 

 portions. 



In Mammalia the middle part of the duct, known as Gaertner's canal, 

 persists in the females of some monkeys, of the pig and of many ruminants. 



The Wolffian body atrophies nearly completely in both 

 sexes ; though, as described above, part of it opposite the testis 

 persists as the head of the epididymis. The posterior part of 

 the gland from the level of the testis may be called the sexual 

 part of the gland, the anterior part forming the non-sexual part. 



