THE TESTICLE. 693 



upper part of the ureter arise small csecal evolutions, which be- 

 come convoluted at certain points and surrounded by mesoblast ; 

 these canals are the urinary tubules, and at the extremity of each 

 is developed a tuft of vessels, which thus forms a Malpighian 

 corpuscle. 



The straight tubes group themselves together at the inner part 

 of the gland, whilst 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 pleuro-peritoneal 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 

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

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

 coming 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 epididyrnis 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 Mullerian 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 

 of the prostate. The upper extremities of the Miillerian ducts 

 form the hydatids of Morgagni. 



The ovary, like the testicle, is formed from the germinal epithe- 



