DEVELOPMENT OF THE WOLFFIAN DUCTS. 



415 



the Mullerian 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 Mullerian 

 and Wolffian ducts, their later 

 history is clear and definite. 

 In all Double-nost rilled (Am- 

 phirhina) and Jaw-mouthed 

 (Gnathostomi) animals, from 

 Primitive Fishes up to Man, 

 the Wolffian duct becomes the 

 seed-duct, and the Mullerian 

 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 (A), female; 

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

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

 Kathke's duct, both formed from the 

 Mullerian duct ; u, primitive urinary 

 duct — acting, in man, also as seed- 

 duct (re) — opening below into Wolff's 

 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 Mullerian 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 

 41 



