176 W. F. E. WEJiDON. 



It therefore seems to me that the organ, whose anatomy I 

 have just described, may very probably have resembled, in its 

 earlier stages, the head kidney described by Wilhelm Miiller, 

 in which case it would have to be regarded as a part of the 

 embryonic kidney, modified, in connection with the needs of the 

 animal, to perform some unknown function in the elaboration 

 or purification of the blood. 



Such a modification of a part of the embryonic kidney is by 

 no means unique amongst vertebrates. In the last paper which 

 he wrote for this Journal, the late Professor Balfour^ showed 

 that, at all events, in a considerable number of Teleostei the 

 head kidney becomes in the adult transformed into a mass of 

 tissue resembling a lymphatic; and he subsequently dis- 

 covered the same modification in the head kidney df 

 Lepidosteus." 



This being the case, the question arises whether there may 

 not exist, in all vertebrate animals, similarly modified portions 

 of the primitive kidney. I believe that such structures 

 are, as a matter of fact, to be found in the suprarenal 

 bodies. 



Though this view of the nature of the suprarenals is by no 

 means in accordance with that generally held, none of the facts 

 at present known concerning either their adult relations or their 

 mode of development seem to me to disprove it. 



First, as to their relations in the adult. 



In Elasmobranchs there are, as Balfour has shown,^ two 

 distinct sets of structures to which the name '' suprarenal 

 bodies " has been applied ; first, a series of paired, appar- 

 ently glandular bodies, arranged segmentally, and each con- 

 nected with a sympathetic ganglion; these bodies, first accurately 

 described by Leydig,* are attached on each side to the dorsal wall 



^ Balfour, on the Structure of the Organ known as the Head Kidney in 

 Teleostei, this Jour., 1882. 



- "On the Structure and Development ofLepidosteus osseus," byF. 

 M. Balfour and W. N. Parker, ' Phil. Trans./ 1882. 



* ' Elasmobranch Fishes.' 



* Rochen uud Haie, Leipzig, 1852, ' Untersuchungen iiber Fische und 

 Beptilien, 1853. 



