RENAL AND EEPEODUCTIVE SYSTEMS. 353 



become converted into accessory genital organs and genital 

 ducts. Owing to the close connection of the two systems, they 

 may, in the adult, be conveniently considered together, though 

 it must be remembered that the connection is merely a 

 secondary one (c/. pp. 254-255). 



In the male rabbit the pronephros is absent or abortive ; 

 the mesonephros, or Wolffian body, acquires an intimate 

 connection with the testis, and becomes converted into the 

 caput epididymis, the proximal part of the Wolffian duct 

 becoming converted into the cauda epididymis, while its distal 

 portion becomes the vas deferens. 



In the female, the pronephros is absent ; the Miillerian 

 duct becomes the oviduct ; the mesonephros or Wolffian 

 body and its duct are absent, or abortive. 



In both sexes alike, the metanephros and its duct become 

 the kidney and ureter respectively. 



The bladder of the rabbit arises as a ventral diverticulum 

 of the rectum, and is at first entirely independent of the 

 kidney ducts, which open into the dorsal wall of the rectum, 

 a condition retained throughout life in the frog. During 

 development the ducts shift round so as to open into the 

 bladder, which then separates from the rectum and acquires 

 a separate opening to the exterior, through which the urinary 

 and genital products leave the body. 



It is convenient to describe the two sexes separately, as 

 they differ very greatly ; and to include in the account certain 

 glands in the neighbourhood of the rectum. 



A. The Male Rabbit. 



1. The renal system. 



a. The kidneys are a pair of dark red bodies about an 

 inch and a quarter long, imbedded in fat in the 

 dorsal wall of the abdomen, outside the peri- 

 toneum. Each is of a flattened ovoid shape, with 

 a notch, the hilus, on its inner side where the 

 ureter and blood-vessels enter and leave it. 



Bisect one of the kidneys, longitudinally, from its outer 



A A 



