6i6 



Fig- 473- — A diagram of the kidney tubules and ducts of \^ertebrata. 



Condition in larva of fishes and amphibians (pronephric tubules shown with separate glomeruli.) 

 op. rud., Developing rudiment of mesonephros ; pn., pronephros; seg.d., segmental duct. B., 

 Condition m adult fishes and amphibians. G., gonad ; op'., part of the mesonephros which in the 

 male is connected with the testis ; op"., part of the mesonephros which is purelv urinary in both 

 sexes ; ur.d., urinary duct of male dogfish and newt ; v.e., vasa efferentia : W.'d., Wolffian duct. 

 C., Condition in the embryos of reptiles, birds, and mammals, after the degeneration of the pronephros. 

 G., gonad ; tnes'., part of the mesonephros which in the male becomes connected with the testis; 

 mes ., rest of mesonephros ; met. rud., rudiment of metanephros ; ur., rudiment of ureter ; W.d., 

 Wolffian duct. D., Condition in the adult of reptiles, birds, and mammals, ep., in male, epididymis, in 

 female a vestige known as epoophoron ; G., gonad ; mes.v., vestige of hinder part of mesonephros, 

 known in male as paradidynus, in female as paroophoron ; met., metanephros (possibly formed by the 

 branching of one tubule only); ur., ureter ; v.d., vas deferens (in male only). 



