URINOGENITAL ORGANS. 



293 



tr 



pass into a second longitudinal canal (Fig. 163) placed near the meso- 

 nephros.and called the longitudinal canal of the mesonephros (absent in 

 Spelerpes, Batrachoseps, etc.). This sends off transverse canals, which 

 correspond in number with the primary rt>nal tubules in the part of the 

 kidney involved in the testicular connection and open into the malpighian 

 bodies of these tubules. So that the sperm passes through the renal tubules 

 of the mesonephros into the mesonephric duct. The nephrostomes of 

 these sexual tubules atrophy in the adult of all male Urodeles except 

 Spelerpes ; but are present in this region in the young form and in the 

 female. The sexual part of the kidney varies much in length. In Siredon 

 as many as 32 primary tubules are connected with the testis. It is much 

 reduced in Spelerpes. A vestige of the miillerian duct is generally present 

 in male Amphibia ; and rudiments of the testicular network can fre- 

 quently be detected in the female (Fig. 163 b). The collecting tubules 

 of the metanephros are directed backward and join into one or more short 

 ducts (ureter) before opening into the mesonephric duct. In Batrachoszpv 

 the first collecting tube is specially 

 developed and receives all the other 

 collecting tubes of the metane- 

 phros. In the female of all Urodeles 

 and in the males of Proteus, Meno- 

 branchus and Siren the collecting 

 tubes retain their transverse course 

 and open direct into the mesone- 

 phric duct. In rare cases the 

 ureter opens direct into the cloaca. 



In the Gymnophiona the kidney 

 is narrow and elongated, extending 

 almost the whole length of the 

 body cavity. The primary tubules 

 are segmentally arranged, but many 

 of them become compound in the 

 adult. There is but little indication 

 of differentiation into meso- and 

 metanephros, and the testicular 

 network is joined to the kidney 

 some little distance behind its 



front end (Fig. 165). The nephrostomes both of the sexual and non- 

 sexual part of the kidney persist in the adult. 



In the Anura the kidney is compact, and the sexual part is not marked 

 off from the rest. There is a testicular network which in Bufo, etc., is 

 connected with some of the malpighian bodies (Fig. 166). In Rana the 

 transverse canals which leave the longitudinal canal of the mesonephros, 

 pass through the kidney and open into the collecting tubes of the renal 

 tubules. In Bombinator the longitudinal canal runs through the kidney 

 and opens into the anterior end of the kidney duct which curves round 

 the front end of the kidney ; the transverse canals end blindly in the 

 substance of the kidney. In Discoglossus a canal arises from the front 

 end of the testis and passes round the front end of the kidney to be con- 

 tinued into the anterior end of the ureter. This canal appears to be the 

 only representative of the testicular network. In Alytes the arrangement 

 is very peculiar and differs from that of all other Anura (Fig. 167). There 

 is a ureter (fused metanephric collecting tubes) passing out from the hind 



FIG 164. Malpighian body and nephrostome 

 of a kidney tubule of Proteus (after Spengel). 

 tr, Nephrostome ; trg, peritoneal canal ; mk 

 malpighian body, and 2 beginning of con- 

 torted tubule of the sexual part of the kidney ; 

 mk' stalk of malpighian body. 



