690 MANUAL OF PHYSIOLOGY. 



From the metanephros a projection arises, which grows quickly, 

 and opens into the cloaca ; this remains as the ureter. From the 

 upper part of the ureter arise small csecal evolutions, which 

 become convoluted at certain points and surrounded by meso- 

 blast ; these canals are the urinary tubules, and at the extremity 

 of each is developed a tuft of vessels, which thus forms a Mal- 

 pighian corpuscle. 



The straight tubes group themselves together at the inner part 

 of the gland, while the convoluted tubules, with the Malpighian 

 corpuscles, are aggregated at the periphery of the gland. 



At the junction of the ureter to the glandular mass, changes 

 take place by which this tube is split up into several subdivisions, 

 which are the primary calices of the kidney, the dilated part of 

 the ureter forming the pelvis. 



The testicle arises partly from the germinal epithelium lining 

 the inner extremity of the pleuroperitoneal cavity, lying close to 

 the splanchnopleure, and partly from the mesoblast surrounding 

 the Wolffian body. 



The germinal epithelium, the cells of which are not so well 

 developed as in the female, sends processes into the mesoblast, 

 and these are said to form the spermatic cells, the mesoblast 

 becoming differentiated around them to form the walls of the 

 tubuli seminiferi. 



The Wolffian duct, which persists as the vas deferens, aids in 

 forming the testicle, the epididymis being merely a convoluted 

 part of it, and the vas aberrans one of the csecal tubes in con- 

 nection with the duct. The coni vasculosi are thought to be 

 formed from some of the tubules of the Wolffian body ; they 

 are connected to the testicle by means of a tube, which is 

 itself split up into a number of divisions which form the 

 vasa efferentia. 



The Wolffian duct forms, besides the vas deferens, the vesicula 

 seminalis (which is merely a blind diverticulum from its extrem- 

 ity), and terminates in the ejaculatory duct. 



The two Miillerian ducts, in the male, join and form a single 

 tube ; this is not further developed, but atrophies, leaving as its 

 representative the sinus pocularis, which is situated in the floor 



