2o6 THE BIOLOGY OF THE FROG chap. 



nected with the collecting tubules which extend across the 

 dorsal side of the kidney to the ureter. The short tubes 

 which connect the longitudinal canal with the collecting 

 tubules widen out near the latter to form an ampulla. This 

 enlargement is formed by a Malpighian body which has lost 

 its glomerulus and consequently its original function. In 



Rana fusca there is a compara- 

 tively direct connection estab- 

 <+----;?a«=\/^F^ plP±:r-N lished between the vasa effe- 



rentia and the collecting tubules, 

 and the spermatozoa, therefore, 

 are not found in the Malpighian 

 "-v.e. bodies and functional renal tu- 

 FiG. 56. - Diagram to illustrate ^^j^^^ Bidder's canal occurs in 



the course of the spermatozoa 



through the kidney of Rana the kidneys of both sexeS, but 



fusca. a, ampulla; ^.collect- j^g function in the female is not 



ir.g tubule ; /, Bidder's longi- 

 tudinal canal; /, uriniferous KUOWn. 



tubule; u, ureter; v.e, vas In many of the lower verte- 



efferens. (Modified from , /t^i i i a 



Beissner.) brates (Elasmobranchs, Am- 



phibia) the kidney is divided 

 mto an anterior, or sexual portion, and a posterior, or ex- 

 cretory portion. The frog presents only the beginning of 

 such a differentiation. The vasa efferentia are connected 

 with the anterior part of the kidney, but the excretory func- 

 tion of this region is still retained. The course of the sper- 

 matozoa through the kidney varies considerably in different 

 species of frogs, as is evinced by the fact that it is much 

 more direct in Rana fusca than in R. escidenta. The latter 

 presents, doubtless, the more primitive condition. 



The kidney is supplied with blood from two different 

 sources: (i) the renal arteries, which rise from the urino- 

 genital arteries, or direct from the aorta, and (2) the renal 

 portal veins^\y\i\c\\. convey venous blood from the posterior 



