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more efficieut elimiDation of excretory matter in the higher groups, 

 such as, for example, a complete double circulation, warm blood, and 

 in the mammals sweat glands. The only inference to be drawn from 

 these facts is that the possession of a renal -portal system indicates 

 a primitive condition of the circulatory system. 



The second objection is based on a consideration of those ab- 

 normalities in which owing to the absence of venae renales advehentes, 

 one kidney does not possess a renal portal circulation in conjunction 

 with the general physiological law that the size of an organ is pro- 

 portional to the work done. The point of the objection lies in the 

 statement that "The two kidneys in these abnormal frogs were in 

 every case [i. e. two (22) and (19)J equal in size". This statement 

 first called my attention to the matter, for in my own two specimens 

 the kidneys were not equal in size. We now have on record five 

 such cases of unequally supplied kidneys, two (8) and (19) in which 

 we can only judge from the diagrams, but even here it will be found 

 that the kidney with a portal supply is depicted as larger than the 

 other, and three in which I have been able to take measurements 

 viz: specimens A and C described by myself and the specimen de- 

 scribed by Dr. Woodland (22) i). 



In order to shew this difiference I have given a diagram Fig. 4, 

 which I made in the following way. The kidneys were photographed 

 in situ and from the print obtained I traced the outlines given. It 

 will be seen that in each case the kidney with a portal supply is 

 longer and wider than the other, and this larger area is accompanied 

 by a slightly thicker body so that the volumes of the two vary con- 

 siderably. This difference, in volume in three of the examples (and 

 possibly in all five) is, I think, too great to be explained by the mere 

 mechanical increase of vascular connections through the kidney sub- 

 stance; nor can it be explained as due to variability; for in not one 

 case out of twenty normal animals I measured did such a difiference 

 of length, breadth and thickness occur as is visible in the kidneys of 

 the three abnormal frogs. It is significant that it is always the kidney 

 with a portal supply that is the larger one. All the evidence derived 

 from the study of abnormalities is clearly opposed to Woodland's 



the appearance in the ancestor of the mammals of a direct anastomosis 

 between the afferent and efferent systems and 2) the ascension of the 

 kidney in the abdominal cavity. 



1) This specimen is preserved in the Zoological Museum University 

 College. 



