DEVELOPMENT OF THE WOLFFIAN DUCTS. 415 



the Miillerian ducts. The latter (Fig. 320, w) lies imme- 

 diately inside the former (Fig. 320 m\ Both open pos- 

 teriorly into the cloaca. 



Obscure and uncertain as 

 is the origin of the Miillerian 

 and Wolffian ducts, their later 

 history is clear and definite. 

 In all Double-nostrilled (Am- 

 phirhina) and Jaw-mouthed 

 (Gnathostomi) animals, from 

 Primitive Fishes up to Man, 

 the Wolffian duct becomes the 

 seed-duct, and the Miillerian 

 duct, the oviduct. In each 

 sex only one of these is per- 



FIGS. 322, 323. Urinary and sexual 

 organs of an Amphibian (Water- Newt, 

 or Triton). Fig. 322 (.4), female; 

 Fig. 323 (B), male : r, primitive kid- 

 ney ; ov, ovary ; od, egg-duct and 

 Eathke's duct, both formed from the 

 Miillerian duct ; u, primitive urinary 

 duct acting, in man, also as seed- 

 duct (re) opening below into Wolffs 

 duct (u') ; ms, ovary-mesentery (mes- 

 ovarium). (After Gegenbaur.) 



sistent ; the other entirely disappears, or leaves only a 

 remnant as a rudimentary organ. In the male sex, in 

 which the two Wolffian ducts become sperm-ducts, certain 

 rudiments of the Miillerian duct are often found, which 

 we will call " Rathke's canals " (Fig. 323, c). In the female 

 sex, where, on the contrary, the two Mullerian ducts 



