EXCRETORY ORGANS. 735 



products pass out by it, and the partial or complete formation 

 of the MiillerSan duct in the male in these cases needs to be 

 explained. This may be done either by supposing the Ganoid 

 arrangement to have been the primitive one in the ancestors of 

 the other forms, or, by supposing characters acquired primitively 

 by the female to have become inherited by both sexes. 



It is a question whether the nature of the generative ducts of 

 Teleostei can be explained by comparison with those of Ganoids. 

 The fact that the Miallerian ducts of the Teleostea-n Ganoid 

 Lepidosteus attach themselves to the generative organs, and thus 

 acquire a resemblance to the generative ducts of Teleostei, 

 affords a powerful argument in favour of the view that the 

 generative ducts of both sexes in the Teleostei are modified 

 Miillerian ducts. Embryology can however alone definitely 

 settle this question. 



In the Elasmobranchii, Amphibia, and Amniota the male 

 products are carried off by the Wolffian duct, and they are 

 transported to this duct, not by open peritoneal funnels of the 

 mesonephros, but by a network of ducts which sprout either 

 from a certain number of the Malpighian bodies opposite the 

 testis (Amphibia, Amniota), or from the stalks connecting the 

 Malpighian bodies with the open funnels (Elasmobranchii). 

 After traversing this network the semen passes (except in 

 certain Anura) through a variable number of the segmental 

 tubes directly to the Wolffian duct. The extent of the con- 

 nection of the testis with the Wolffian body is subject to great 

 variations, but it is usually more or less in the anterior region. 

 Rudiments of the testicular network have in many cases become 

 inherited by the female. 



The origin of the connection between the testis and Wolffian body is still 

 very obscure. It would be easy to understand how the testicular products, 

 after falling into the body-cavity, might be taken up by the open extremities 

 of some of the peritoneal funnels, and how such open funnels might have 

 groove-like prolongations along the mesorchium, which might eventually be 

 converted into ducts. Ontogeny does not however altogether favour this 

 view of the origin of the testicular network. It seems to me nevertheless the 

 most probable view which has yet been put forward. 



The mode of transportation of the semen by means of the mesonephric 

 tubules is so peculiar as to render it highly improbable that it was twice 

 acquired, it becomes therefore necessary to suppose that the Amphibia and 



