ON THE SUPEAEENAL BODIES OP VEETEBEATA. 189 



distance from any vessel, and the later tissue only approaching 

 one when it has so greatly increased in size as to have pushed 

 all the intervening mesoblast, so to speak, on one side. There 

 is no possibility of believing, in this case at least, that the 

 walls of the blood-vessels have the slightest share in the pro- 

 duction of the cortical blastema. 



The great difference between the results of the investigations 

 of previous observers and those which have just been described, 

 is suflSciently obvious. If, however, the accuracy of mj 

 observations be admitted, we have a much more rational expla- 

 nation of the phylogeny of the suprarenals than is possible if 

 we adopt the view of Braun, and others ; — an explanation which 

 receives support, both from the anatomical relations of the 

 adult organs, and with those of the corresponding organs in 

 Myxinoids and Teleosteans. 



InBdellostoma, I have already^ attempted to show that 

 the head kidney has become modified so as to form an organ 

 functionally analogous to the suprarenals; while in Teleos- 

 teans, a most remarkable series of modifications, affecting 

 every region of the kidney, has been described by Balfour and 

 Emery; a series which seems to me to supply every stage 

 needful to complete our conception of the passage from such a 

 form as Bdellostoma to that of a higher vertebrate. Balfour 

 showed^ that the head kidney of many adult Teleosteans con- 

 sisted, not of renal tissue, but of a mass of parenchymatous 

 "lymphatic" material, richly supplied with vessels, whose 

 function, whatever it might be, was certainly not that of a 

 normal kidney. He afterwards found the same kind of modi- 

 fication to exist in the head kidney of the Teleosteoid 

 Ganoids.* 



Though the observations of Balfour left it highly probable 

 that the " lymphatic " tissue described by him was really a 

 result of the transformation of part of the embryonic kidney, 



1 Quart. Journ. Mic. Sci., April, 1884. 



2 Quart. Journ. Mic. Sci., 1882. 



3 "On the Structure and Development of Lepidosteus," 'Phil. Trans., 



1882. 



