MALE REPRODUCTIVE SYSTEM OF AMPHIBIA 241 



MALE REPRODUCTIVE SYSTEM OF AMPHIBIA. 



The testes are more or less elongated, tubular bodies in the 

 urodeles and lower forms, and ovoid in anurans. They are ovoid, 

 yellowish-white bodies lying alongside or ventral to the kidneys 

 and connected to the latter by a mesenteric sheet of tissue. Each 

 testis is a mass of tubules fitting the general descri])tion given for 

 the seminiferous tubules. The seminiferous tubules connect with 

 the vasa efferentia, derived from embryonic mesonephric tubules 

 and supported by mesentery. When the efferentia reach the 

 functional kidney they pass into a longitudinal duct, Bidder's canal, 

 which runs along the mesial border of the mesonephros. (Fig. 148.) 



Fig. 148. — Longitudinal section of testis of Necturus, showing seminiferous tubules 

 radiating toward ducts in connective tissue below. 



During development of anurans, an anterior part of the testis, 

 possibly derived from pronephric tissue, has large cells resembling 

 oocytes or enlarged spermatocytes. This structure. Bidder's organ, 

 may persist well into the mature stage of toads, but gradually 

 degenerates. The remains of the ])ronephric ducts passing along 

 the mesonephros form Bidder's canal. Its lumen is lined with 

 columnar epithelium supported by a connective tissue and a few 

 smooth muscle cells. The outermost region of the canal has con- 

 nective tissue continuous with that of the covering of the kidney in 

 which it is partially embedded. 



Bidder's canal communicates with the collecting tubules in the 



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