RATA. 319 
The chief organs now remaining in the abdominal cavity 
belong to the urogenital system. ‘The excretory and repro- 
Urogenital ductive organs of vertebrates are so intimately 
* connected that they are usually described in this 
way as one system. 
In the male, the Zestes 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 nat.) 
Mesonephros (Epididymis). 
Vasa Efferentia. 
“Mesonephric 
uct. 
Metanephros 
(Kidney). 
Seminal Vesicle. 
‘Sperm-sac. 
Urogenital Papilla. ~ 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 uzo- 
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 pazrved elongated reddish bodies lying 
above the abdominal cavity, and they can be dissected by 
