4SS 



CHORDATA. 



type occurriii!^ most al.niinlantly in the posterior part of the mesonephros, 

 and leading some to regard this portion as a metanephros. 



The metanephros, in its typieal form as it appears in tJie amniotes, 

 consists of two anhagen. A canal grows out from the Wolllian duct, 

 extends craniahvard, and liranches richly at its anterior end. The canal 

 is the iirckr, the tubules arising from it are the so-called straight tubules 



B 



Ov- 



m/(Ut/) 



Fig. 530. — Scheme of uroilclc urogenital sy<;tein based on Triton ifrom Wicdcrs- 

 heim, after Spe)ij,'el), .1 , male; B, female, j, excretory iluets; ,!;», sexual part of meso- 

 nephros; Ho, testis; /s;, Leyilig's duct (ureter); )»,i^, :Miillerian duct (.oviduct); nif,' . its 

 vestigial end in male; N , functional part of mesonephros; Or, ovarv; (">/, ostium tuba-; 

 TV, ^■asa cfferentia; *, collecting duct of vasa elTerentia (.rudimentary in B). 



of the kidney. The other part of the organ coirsists of tubules, which 

 arise from 'nephrogenic tissue,' have no nephrostomes, but include a 

 Malpighian body at the end. The other end connects with the straight 

 tubules. They form the convolutetl tubules of human histology. 



