7IO AMPHIBIA. 



Before dealing with the further changes of the Wolffian body 

 it is necessary to return to the segmental duct, which, at the 

 time when the pronephros is undergoing atrophy, becomes split 

 into a dorsal Wolffian and ventral Mlillerian duct. The process 

 in Salamandra (Fiirbringer) has much the same character as in 

 Elasmobranchii, the Mullerian duct being formed by the gradual 

 separation, from before backwards, of a solid row of cells from 

 the ventral side of the segmental duct, the remainder of the duct 

 constituting the Wolffian duct. During the formation of the 

 Mullerian duct its anterior part becomes hollow, and attaching 

 itself in front to the peritoneal epithelium acquires an opening 

 into the body cavity. The process of hollowing is continued 

 backwards pari passu with the splitting of the segmental duct. 

 In the female the process is continued till the Mullerian duct 

 opens, close to the Wolffian duct, into the cloaca. In the male 

 the duct usually ends blindly. It is important to notice that 

 the abdominal opening of the Mullerian duct in the Amphibia 

 (Salamandra) is a formation independent of the pronephros, and 

 placed slightly behind it ; and that the undivided anterior part 

 of the segmental duct (with the pronephros) is not, as in Elasmo- 

 branchii, united with the Mullerian duct, but remains connected 

 with the Wolffian duct. 



The development of the Mullerian duct has not been satisfactorily 

 studied in other forms besides Salamandra. In Cceciliidas its abdominal 

 opening is on a level with the anterior end of the Wolffian body. In other 

 forms it is usually placed very far forwards, close to the root of the lungs 

 (except in Proteus and Batrachoseps, where it is placed somewhat further 

 back), and some distance in front of the Wolffian body. 



The Mullerian duct is always well developed in the female, and serves as 

 oviduct. In the male it does not (except possibly in Alytes) assist in the 

 transportation of the genital products, and is always more or less rudimen- 

 tary, and in Anura may be completely absent. 



After the formation of the Mullerian duct, the Wolffian duct 

 remains as the excretory channel for the Wolffian body, and, till 

 the atrophy of the pronephros, for this gland also. Its anterior 

 section, in front of the Wolffian body, undergoes a more or less 

 complete atrophy. 



The further changes of the excretory system concern (i) the 

 junction in the male of the anterior part of the Wolffian body 

 with the testis ; (2) certain changes in the collecting tubes of the 



