36a 



theory, and points to the greater functional activity of the kidney 

 supplied by a portal vein. 



Shore (17 and 20) states that the sinus-like system of the kidney 

 arises by a penetration of the mesouephric tubules into the cardinal 

 vein ; while the sinoilar system of the liver is produced by the erup- 

 tion of capillary blood vessels from the vitelline vein into the mass 

 of hypoblast^). Woodland accepts and emphasizes this difference of 

 origin and closes his third argument: "If we assume as we logically 

 must, that a given function will, under similar conditions, always be 

 performed iu the same manner, then, on this account alone, the ob- 



E. 



W. 



Fig. 4. Kidneys of Abnormal Frogs. To show the relative sizes of the organ 

 with a renal-portal supply and that without. 



I. Specimen A. II. Specimen B. III. Woodland's Specimen. 



vious inference is that the 'sinus-like system' forming the connection 

 between the posterior cardinal and post-renal veins has nothing what- 

 ever to do with the elimination of excretory matter from the blood". 

 This is a confusion of homology and analogy; for although the origin 

 may differ, the function performed may be similar. According to 

 Lewis "Sinusoids have been demonstrated histologically and embryo- 

 logically in the Wolffian body, the myocardium and the Hver", a point 



1) It is to be noted however in connection with this question of 

 "Sinusoids" that Minot (13) and Lewis (11) in more recent papers than 

 that of Shore maintain that the sinusoids of the liver and mesonephros 

 develop in essentially the same way. 



