440 PROCEEDINGS OF THE CANADIAN INSTIRUTE. 
complete ring around it. The largest and most constant of these: 
bodies lies on the right side between the gall-bladder and spleen and 
close to the mesenteric artery. It does not surround any large ves- 
sel, but lixe the rest of these bodies is well supplied with blood. 
Where these bodies were cut in sections through the head-kidney 
and spleen they closely resembled the suprarenal bodies in their 
histological structure, but in sections through others the difference: 
was quite marked. The most important feature was the presence of 
spaces surrounded by a connective tissue wall, and having either a 
process or a central mass of the ordinary tissue connected by small 
processes with the surrounding wall. The blood-vessels pass to the 
centre through these. The interspaces seem to be occupied by a 
loose unattached tissue. 
It seems probable from the relationship of these structures to the: 
surface of the veins that they belong to the lymphatic system, and 
as lam unable at present to investigate this part of the vascular 
system of Amiwrus, I shall say nothing further in regard to them. 
THE URO-GENITAL SYSTEM. 
THE KIDNEY. 
The kidney has been carefully described in a number of Siluroids. 
by Hyrtl', Although this organ in Amiwrus agrees closely with 
these—especially with that of Stlurus glanis—it will not be out of 
place to give a somewhat detailed account of it in this paper. 
It is divided into an anterior lymphatic portion, the ‘ head-kidney” 
and a posterior portion, the functional or true kidney. These two- 
divisions are separated by the entire length of the air-bladder, around 
the anterior and posterior ends of which they mould themselves. 
These three organs fill the entire dorsal portion of the body cavity 
from the aponeurotic membrane of the pectoral girdle to its posterior 
extremity, and present a smooth level ventral surface covered by 
peritoneum. 
The head-kidney (pronephros), is a paired organ, the two halves of 
which are joined by a bridge of gland substance crossing beneath the 
first, second and third vertebre. The bulk of the gland lies above 
this bridge, filling the space between the transverse process ot the 
1 Sitz. Weiner Akd. 1851. 
