UROGENITAL SYSTEM 



815 



forms, as this : In the cyclostomes the eggs are thrown from the ovaries 

 directly into the coelom, being passed out through abdominal pores, but 

 in the teleosts alone there are several conditions, the ovaries of some are 



B 



testis 

 vasa efferentia 



tpididymis (vestige 

 f mesonephros) 



metanephros 



Fig. 458. 



Diagrams to illustrate the urogenital system of male and female anamniotes and 

 amniotes. A, male elasmobranch or amphibian ; the mesonepheros is differentiated 

 into anterior genital and posterio-excretory portions ; the genital part is connected 

 with the testis by means of the vasa efferentia, which are outgrowths from the 

 mesonepheros, the mesonepheric or WolfRan duct serves as both genital and ex- 

 cretory duct ; the oviduct or Miillerian duct is vestigial. B, female elasmobranch or 

 amphibian ; the ovary is not qonnected with the mesonephros ; the mesonephros 

 and mesonephric duct serve only excretory functions ; the oviduct is well developed 

 and opens into the coelom by the ostium near the ovary. C, male reptile, bird, or 

 mammal. The excretory part of the mesonephros has disappeared but the genital 

 part persists as the epididymis (in part) which is connected as in anamniotes with 

 the testis by means of the vasa efferentia ; the Wolffian duct is purely genital and 

 is renamed the vas deferens ; the excretory function is served by the metanephroi 

 and ureters. D, female reptile, bird or mammal ; the mesonephros and Wolffian 

 duct have entirely vanished ; the condition of the ovary and oviduct is the same 

 as in anamniotes ; the excretory function is served by the metanephroi and ureters 

 exactly as in the male. (From Hyman's modification of Wilder.) 



