THE DOGFISH 



355 



of these is rudi- 

 mentary and dis- 

 appears early in 

 development. The 

 mesonephros is a 

 long, narrow organ, 

 which in the adult 

 female is reduced 

 to a mere vestige 

 and can only be 

 found by removing 

 the peritoneum, 

 but in the male is 

 better developed 

 and, with its duct, 

 makes a ridge 

 along the body 

 cavity. Its collect- 

 ing tubules open 

 directly into the 

 Wolffian duct. The 

 metanephros is a 

 larger organ which 

 forms a cushion- 

 like swelling and 

 is the principal 

 excretory organ in 

 both sexes ; its 

 collecting tubules, 

 as will presently 

 be explained, dis- 

 charge into ducts 

 of their own, which 

 in the male do not 

 enter the Wolffian 

 duct. It is not 



.-■/■«■ 



'«./>■ 



Fig. 254. — The reproductive organs of a female 

 dogfish. 



Seen m the frog, c/> Cloaca; fj. t part of the "falciform ligament 

 where the whole i.o.d., internal opening of the oviducts ; msn., meso- 



nephros; msov., mesovarium ; mtn., metanephros; 

 o.d., oviduct; oes. t oesophagus; ov., ovary; rm. 

 rectum ; sh. t shell gland ; ur"., ducts of metanephros 

 u.£., urinary papilla; km., urinary sinus; W.d 

 Wolffian duct. 



kidney is mesone- 

 phric. • A duct, — 

 the mesonephric or 



