EXCRETORY ORGANS. 697 



manent kidney or metanephros of the amniotic Vertebrates, and 

 for this reason the numerous collecting tubes or single collecting 

 tube, as the case may be, will be spoken of as ureters. The 

 anterior tubuli of the primitive excretory organ retain their early 

 relation to the Wolffian duct, and form the permanent Wolffian 

 body or mesonephros. 



The originally separate terminal extremities of the Wolffian 

 ducts always coalesce, and form a urinal cloaca, opening by a 

 single aperture, situated at the extremity of the median papilla 

 behind the anus. Some of the peritoneal openings of the seg- 

 mental tubes in Scyllium, or in other cases all the openings, 

 become obliterated. 



In the male the anterior segmental tubes undergo remark- 

 able modifications, and become connected with the testes. 

 Branches appear to grow from the first three or four or more of 

 them (though probably not from their peritoneal openings), 

 which pass to the base of the testis, and there uniting into a 

 longitudinal canal, form a network, and receive the secretion of 

 the testicular ampullae (fig. 393, nf). These ducts, the vasa 

 efferent ia, carry the semen to the Wolffian body, but before 

 opening into the tubuli of this body they unite into a canal 

 known as the longitudinal canal of the Wolffian body (l.c\ from 

 which pass off ducts equal in number to the vasa efferentia, 

 each of which normally ends in a Malpighian corpuscle. From 

 the Malpighian corpuscles so connected there spring the con- 

 voluted tubuli, forming the generative segments of the Wolffian 

 body, along which the semen is conveyed to the Wolffian duct 

 (v.d). The Wolffian duct itself becomes much contorted and 

 acts as vas deferens. 



Figs. 392 and 393 are diagrammatic representations of the 

 chief constituents of the adult urinogenital organs in the two 

 sexes. In the adult female (fig. 392), there are present the 

 following parts : 



(1) The oviduct or Mullerian duct (m.d) split off from the 

 segmental duct of the kidneys. Each oviduct opens at its 

 anterior extremity into the body cavity, and behind the two 

 oviducts have independent communications with the general 

 cloaca. 



(2) The mesonephric ducts (w.d), the other product of the 



