EXCRETORY ORGANS. 



7'3 



connected with a rudimentary testicular network, and a posterior 

 part. The collecting tubes from both 

 parts fall transversely into the Wolf- 

 fian duct. 



(4) The ovary (ov). 



(5) The rudimentary testicular 

 network. 



In the male (B) the following 

 parts are present : 



(1) The functionless though fairly 

 developed Miillerian duct (;). 



(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 into it close to its cloacal aper- 

 ture, after uniting to form one or two 

 primary tubes (ureters). 



(4) The testicular network (ve) 

 consisting of (i) transverse ducts 

 from the testes, falling into (2) the 

 longitudinal canal of the Wolffian 

 body, from which (3) transverse ca- 

 nals are again given off to the Mal- 

 pighian bodies. 



Amniota. The amniotic Verte- 

 brata agree, so far as is known, very 

 closely amongst themselves in the 

 formation of the urinogenital system. 



The most characteristic feature of the system is the full 

 development of a metanephros, which constitutes the functional 

 kidney on the atrophy of the mesonephros or Wolffian body, 

 which is a purely embryonic organ. The first part of the 

 system to develop is a duct, which is usually spoken of as the 

 Wolffian duct, but which is really the homologue of the seg- 



FIG. 400. DIAGRAM OF THE 

 URINOGENITAL SYSTEM OF TRI- 

 TON. (From Gegenbaur ; after 

 Spengel.) 



A. Female. B. Male. 

 r. mesonephros, on the surface 

 of which numerous peritoneal fun- 

 nels are visible ; sug. mesonephric 

 or Wolffian duct; od. oviduct 

 (Miillerian duct); in. Miillerian 

 duct of male ; ve. vasa efferentia of 

 testis ; t. testis ; ov. ovary ; up. 

 urinogenital pore. 



