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spindle-cells of a doubtful character. The surface is irregularly infolded, 
and the body contains many venous spaces with blood corpuscles. - 
Itis just possible that these bodies were once glandular, but have 
degenerated. Whether they have anything to do with suprarenal bodies 
we cannot say. 
? Petromyzon Planeri. 
Similar structures to those found in P. marinus were seen in 
this species, excepting the oval-shaped body lying between the dorsal 
wall of the sinus venosus and the ventral wall of the dorsal aorta. 
The triangular bands of connective tissue noticed by ECKER are here 
very much smaller than in P. marinus. 
Ammocoetes. 
In specimens of Ammocoetes the “white-bodies” of RATHKE 
were found, agreeing in all respects with his description. -They were 
considerably larger than those found in the adult Petromyzon 
marinus. 
Summary and Conclusion. 
Briefly summarising the results, we are of opinion: 
1) That there is no satisfactory evidence of any suprarenal bodies in 
the Cyclostoma. 
2) That the bodies described by ECKER are purely connective tissue, 
possibly an osteogenetic tissue. 
3) The ‘“‘white-bodies” and ‘“‘bullet-shaped bodies” of RATHKE also 
consist of connective tissue. 
4) The body described by JOHANNES MULLER as suprarenal, later 
as thymus, is the pronephros, which is present in Myxine and 
Bdellostoma, but absent in Petromyzon. 
5) As yet there is no evidence which would lead us to 
suppose that the pronephros of Cyclostoma repre- 
sents the suprarenal bodies of Gnathostoma, and the 
theory put forward by RATHKE, and reiterated by 
WELDON has no evidence in its favour. We would em- 
phasise the fact, that evidence is still wanted to 
prove that there is any relation, beyond that of 
position, between the suprarenal bodies of Verte- 
brates and the renal organs’), the two having widely 
1) In adults at any rate, we can state positively that there is no 
such connection. With regard to the development, there are two rival 
theories concerning the origin of the cortex; one that of WELDoN, accord- 
ing to which this portion of the gland developes from the Wolffian body ; 
the other that of Mrmatxovics, who says it has been derived from the 
germinal epithelium. Not having worked out the development, we do not 
