4/4 DEVELOPMENT OF ELASMOBRANCH FISHES. 



become divided into a ganglionic and a non-ganglionic part, 

 with the same relations as the ganglia and suprarenal tissue in 

 the adult. These grounds appear to me to afford ample justifica- 

 tion for my determinations, and the evidence adduced above 

 appears to me to render it almost certain that the suprarenal 

 tissue is a product of the primitive ganglion and not introduced 

 from the mesoblast without, though it is not to be denied that 

 a more complete investigation of this point than it has been 

 possible for me to make would be very desirable. 



Professor Semper states that he only made a very slight 

 embryological investigation of these bodies, and probably has 

 only carefully studied their later stages. He has accordingly 

 overlooked the branches connecting them with the spinal nerves, 

 and has not therefore detected the fact that they develope as 

 parts of the sympathetic nervous system. I feel sure that if he 

 re-examines his sections of younger embryos he will not fail to 

 discover the nerve-branches described by me. His descriptions 

 apart from this point accord fairly well with my own. The 

 credit of the discovery that these bodies are really derivatives 

 of the sympathetic nervous system is entirely Leydig's : my 

 observations do no more than confirm his remarkable observa- 

 tions and well-founded conclusions. 



I nter renal body, 



My investigations on the interrenal body in the adult are 

 even less complete than those on the suprarenal bodies. I find 

 the body forming a small rod elliptical in section in the poste- 

 rior region of the kidney between the dorsal aorta and unpaired 

 caudal vein. Some little distance behind its front end (and 

 probably not at its thickest point) it measured in one example, 

 of which I have sections, a little less than a millimetre in its 

 longest diameter. Anteriorly it overlaps the suprarenal bodies, 

 and I failed to find any connection between them and it. On 

 this point my observations do not accord with those of Professor 

 Semper. I have however only been able to examine hardened 

 specimens. 



It is, vide PI. 18, fig. 8, invested by a fairly thick tunica 

 propria, which sends in septa, dividing it into rather well-marked 



