28^ Rl^SUMlf OF UROGENITAL SYSTEM. 



the same level, into the hindermost section of the Wolffian duct 

 in the female, or into the urinogenital cloaca, formed by the 

 coalesced terminal parts of the Wolffian ducts, in the male ; or 

 in other species become modified in such a manner as to 

 pour their secretion into a siugle duct on each side, which opens 

 in a position corresponding with the numerous ducts of the 

 other type (woodcut, fig. 8). It seems that both in Amphi- 

 bians and Elasmobranchs the type with a single duct, or ap- 

 proximations to it, are more often found in the females than 

 in the males. The subject requires however to be more 

 worked out in Elasmobranchs \ In both groups the modified 

 posterior kidney-segments are probably equivalent to the per- 

 manent kidney of the amniotic Vertebrates, and for this reason 

 the numerous ducts of the first group or single duct of the 

 second were spoken of as ureters. The anterior tubuli of the 

 primitive excretory organ retain their early relation to the 

 Wolffian duct, and form the Wolffian body. 



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 median papilla 

 behind the anus. Some of the abdominal openings of the 

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

 become obliterated. 



In the male the anterior segmental tubes undergo remark- 

 able modifications. There appear to grow from the first three 

 or four or more of them (though the point is still somewhat 

 obscure) branches, which pass to base of the testis and there 

 unite into a longitudinal canal, form a network, and receive 

 the secretion of the testicular ampullas (woodcut 9, nt). These 

 -ducts, the vasa efferentia, carry the semen to the Wolffian body, 

 but before opening into the tubuli of this they unite into 

 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 body. From the Malpighian 

 body so connected start the convoluted tubuli of what may be 

 called the generative segments of the Wolffian body along 



1 The reverse of the above rule is the case with Raja, in the male of 

 which a closer approximation to the single-duct type is found than in the 

 female. 



