EXCRE TOR Y AND REPRODUCTI VE S YSTEMS. 547 



The segmental duct of each side divides into Wolffian 

 and Miillerian ducts. The Wolffian duct becomes in the 

 male the vas deferens, in the female it is an unimportant 

 Wolffian duct ; the Miillerian duct becomes in the female 

 the oviduct, in the male it is a mere rudiment. 



The muscles and other organs of Elasmobranchs retain 

 considerable quantities of nitrogenous waste products. 



There can be no doubt 

 that the body cavity helps 

 in excretion, and gets rid 

 of waste through the two 

 abdominal pores. In some 

 Elasmobranchs these are 

 replaced by openings (neph- 

 rostomes) into the kidney. 

 Occasionally there are both 

 nephrostomes and abdomi- 

 nal pores. 



The male organs or 

 testes lie on each side 

 of the cardinal sinus, 

 moored by a fold of 

 peritoneum. Sperma- 

 tozoa pass from the 

 testis by vasa effer- 

 entia into a tube sur- 

 rounded anteriorly by 

 epididymis. The tube 

 of the epididymis is 

 continued into the 

 vas deferens, which 

 is 



into a seminal ves- 

 icle and an adjacent 

 sperm - sac. Finally, 

 the two vasa deferentia open into the urogenital sinus, 

 whence the spermatozoa pass into the cloaca. Thence, in 

 copulation, they pass into the complex " claspers " of the 

 male, which are said to be inserted into the cloaca of the 

 female. 



The female organs or ovaries lie on each side of the car- 



FlG. 289. Urogenital organs of female 

 skate. In part after Monro. 



rh'ls Wl nnctprinrl v **"* A P erture of united oviducts ; W.D., Wolffian 

 ^ rl y duct ; ov., ovary ; O.D.G., oviducal gland ; 

 ., egg in mermaid's purse; >L, bladder at 

 base of Wolffian ducts (arrow into cloaca) ; A"., 

 kidney (arrow from base of oviduct into cloaca). 



