359 



returned to the heart by the post-caval must have been returned 

 by the right posterior cardinal. This posterior cardinal during its 

 passage along the kidney gives off venae advehentes as in the 

 specimens described by Howes (10) and perhaps Shore (18). It 

 therefore follows that at any rate some of the blood coming from the 

 lower limb passed through the kidaey. After receiving the branch 

 from the inter-renal, the right posterior cardinal continues forward to 

 open into the innominate ; its relations being very similar to those de- 

 scribed in the first frog; and here again there is a well marked di- 

 latation of the innominate. On the left side it is only the anterior 

 part of the posterior cardinal that persists, that part in fact which 

 runs forward from the junction of the tributary from the inter-renal. 

 It is in a very reduced condition, so that I had difficulty in making 

 out its anterior relations, I was able however to make out that it 

 opens into the internal jugular vein just before this unites with the 

 subscapular. There is on the left side an independent renal portal 

 having no connections with the corresponding posterior cardinal. 



The kidneys did not differ in size in the way that has been no- 

 ticed in the other two cases, for, although the right is somewhat longer 

 than the left, it is at the same time slightly narrower. Then, too, 

 there is not such a conspicuous asymmetry in the factors of the inter- 

 renal vein. 



Part n. 



The relation of these abnormalities to the development 

 of the venous system. 

 The significance of these abnormalities become clear when we 

 consider them in the light of Hochstetter's account (9) of the de- 

 velopment of the venous system in the Amphibia. Briefly stated his 

 views may be put as follows. In the young larval condition the main 

 posterior veins are the two large posterior cardinals, related to the 

 pronephros, which arise as a bifurcation of the caudal vein. On the 

 formation of the mesonephros, the part of the posterior cardinal in 

 relation to it becomes split into a loop which surrounds the kidney, 

 that part on the outside being known as Jacobson's vein. In normal 

 cases the anterior and posterior connections of this loop are lost; 

 while at the same time the two inner parts unite in the middle line 



doubtless due to the much drier climate of Australia, and the consequent 

 inabilitj^ of the frog to make such efficient use of its skin as an organ 

 of respiration. 



