EXCRETORY ORGANS. 



587 



400 B), and tlie collecting tubes tbeniselves unite together into one or 

 more short ducts (ureters) before joining the Wolffian duct. 



In Batrachoseps only tlie first collecting tube becomes split off in 

 this way ; and it forms a single elongated ureter which receives all the 

 collecting tubes of the posterior segmental tubes. In the female and in 

 the male of Proteus, Menobranchus, and Siren the collecting tubes retain 

 their primitive transverse course and open laterally into the Wolffian duct. 

 In rare cases (EUipsoglossus, Spemjel) the ureters open directly into tlie 

 cloaca. 



The urinary bladder of the Ampliibia is an outgrowth of the 

 ventral wall of the cloacal section of the alimentary tract, and is 

 liomologous with the allantois of the 

 amniotic Vertebrata. 



The subjoined diagram (fig. 400) of 

 the urogenital system of Triton illus- 

 trates the more important points of the 

 preceding description. 



In the female (A) the following parts 

 are present : 



(1) The Mlillerian duct or oviduct 

 {od) derived from the splitting of the 

 segmental duct. 



(2) The Wolffian duct {sug) con- 

 stituting the portion of the segmental 

 duct left after the formation of the 

 Mlillerian duct. 



(3) The mesonephros(r), divided into 

 an anterior sexual part connected with 

 a rudimentary testicular network, and a 

 posterior part. The collecting tubes 

 from both parts fall transversely into 

 the Wolffian duct. 



(4) The ovary (ov). 



(0) The rudimentary testicular net- 

 work. 



In the male (B) the following parts 

 are present : 



(1) The functionless though fairly 

 developed Mlillerian duct (m). 



(2) The Wolffian duct {sug). 



(3) The mesonephros (r) divided 

 into a true sexual part, through the 

 segmental tubes of which the semen 

 passes, and a non-sexual part. The 

 collecting tubes of the latter do not 

 enter the Wolffian duct directly, but 

 bend obliquely backwards and only fall urinogen'ital'pore. 



^ A 



Fkj. 403. Diagram of the 



URINOGENITAL SYSTEM OF TrITON. 



(From Gegeiibaur; after Siiengel.) 

 A. Female. B. Male. 

 r. mesonephros, on the surface 

 of which numerous peritoneal fun- 

 nels are visible ; siig. mesonephric 

 or Wolffian duct; od. oviduct 

 (Mlillerian duct) ; m. Miilleriau 

 duct of male ; ve. vasa efferentia 

 of testis; f. testis; ov. ovary; up. 



