RAIA. 319 



The chief organs now remaining in the abdominal cavity 



belong to the urogenital system. The excretory and repro- 



nitai ^^^^iv^ organs of vertebrates are so intimately 



connected that they are usually described in this 



way as one system. 



In the male, the testes are two large pale brown organs 

 lying in the abdominal cavity and suspended by a dorsal 

 mesentery towards their front end. 



Fig. 229. — Male Urogenital Organs of a Skate. {Ad jtat.) 



Mesonephros (Epididymis). 

 Vasa EfFerentia. 



Testis. .- 



Ureters. = 



^Metanephros 



(Kidney). 

 ~» Seminal Vesicle. 



Sperm-sac. 



Urogenital Papilla. ,^''^^^ ^^ . c -n . 



f ^BV Opening of Ureters into 



• Urogenital Sinus. 

 Cloacal Aperture. 



Each testis gives off from its anterior end a long coiled 

 tube, the vas deferens, which passes along on either side of 

 the dorsal middle line to open posteriorly into the uro- 

 genital sinus. Connected with its posterior end is the 

 sperm-sac. The anterior half of the vas deferens is sur- 

 rounded by an epididymis, which is said to be the persistent 

 mesonephros, and the posterior half is in close contact with 

 the surface of the kidney. 



The kidneys are paired elongated reddish bodies lying 

 above the abdominal cavity, and they can be dissected by 



