EENAL AND EEPRpDUCTIVE SYSTEMS. 259 



fins. In the female there are three openings into 

 it : the rectum in front, the genital aperture in the 

 middle, and the urinary sinus behind. 



B. The Male. 



1. The testes are a pair of soft elongated bodies lying along 



the dorsal wall of the abdominal cavity, and in the 

 adult united with each other at their hinder ends. 

 Like the ovary they are attached to the body- wall by 

 delicate folds of peritoneum which are very easily 

 torn, so that in many specimens- the testes appear to 

 lie free in the abdominal cavity. 



2. The vasa efferentia are a number of very slender duets 



which arise on each side from the dorsal surface of 

 the testis, and run forwards in the fold of peritoneum 

 to the Wolffian body, which they enter at its anterior 

 end. 



3. The kidneys. Each kidney is, as in the female, divided 



into an anterior part, the Wolffian body or meso- 

 nephros, forming about half of its entire length ; and 

 a posterior part or metanephros. The mesonephros 

 differs from that of the female in being a well- 

 developed lobulated glandular body along its whole 

 length. The metanephros, as in the female, is a 

 laterally compressed mass of considerable size, 

 especially thick at its hinder end. 



Dissect off the peritoneum from the ventral surface of one 

 of the kidneys, so as to expose it along its ivhole length. At 

 the hinder end dissect the metanephros from the body-wall 

 along its outer side, so as to see its full size. 



4. The WolflSan ducts are a pair of thick-walled tubes 



running in a very sinuous course, one along the 

 ventral surface of the whole length of each Wolffian 

 body, from which it receives numerous segmentally 

 arranged tubules. Opposite the junction of Wolffian 

 body and metanephros it dilates rather suddenly 

 into a wide thin- walled tube, the vesicula seminalis, 



a"2 



