EXCRETORY ORGANS. 



711 



posterior part of the mesonephros. The first of these processes 

 results in the division of the Wolffian body into a sexual and a 

 non-sexual part, and in Salamandra and other Urodeles the 

 division corresponds with the distribution of the simple and 

 compound segmental tubes. 



Since the development of the canals connecting the testes with 

 the sexual part of the Wolffian body has not been in all points 

 satisfactorily elucidated, it will be convenient to commence with a 

 description of the adult arrangement of the parts (fig. 400 B). In 

 most instances a non-segmental system of canals the vasa effc- 

 rentia (ve) coming from the testis, fall into a canal known as the 

 longitudinal canal of the Wolffian body, from which there pass off 

 transverse canals, which fall into, and are equal in number to, the 

 primary Malpighian bodies of the sexual part of the gland. The 

 spermatozoa, brought to the Malpighian bodies, are thence trans- 

 ported along the segmental tubes to the Wolffian duct, and so to 

 the exterior. The system of canals connecting the testis with 

 the Malpighian bodies is known as the testicular network. The 

 number of segmental tubes connected with the testis varies 

 very greatly. In Siredon there are as many as from 30 32 

 (Spengel). 



The longitudinal canal of the Wolffian body is in rare instances 

 (Spelerpes, etc.) absent, where the sexual part of the Wolffian body is 

 slightly developed. In the Urodela the testes are united with the anterior 

 part of the Wolffian body. In the Cceciliidas the junction takes place in an 

 homologous part of the Wolffian body, but, owing to the development of the 

 anterior segmental tubes, which are rudimentary in the Urodela, it is 

 situated some way behind the front end. Amongst the Anura the connection 

 of the testis with the tubules of the Wolffian body is subject to considerable 

 variations. In Bufo cinereus the normal Urodele type is preserved, and in 

 Bombinator the same arrangement is found in a rudimentary condition, in 

 that there are transverse trunks from the longitudinal canal of the Wolffian 

 body, which end blindly, while the semen is carried into the Wolffian 

 duct by canals in front of the Wolffian body. In Alytes and Discoglossus 

 the semen is carried away by a similar direct continuation of the lon- 

 gitudinal canal in front of the Wolffian body, but there are no rudi- 

 mentary transverse canals passing into the Wolffian body, as in Bombi- 

 nator. In Rana the transverse ducts which pass off from the longitudinal 

 canal of the Wolffian body, after dilating to form (?) rudimentary Malpighian 

 bodies, enter directly into the collecting tubes near their opening into the 

 Wolffian duct. 



