440 PROCEEDINGS OF THE CANADIAN 1NSTIRUTE. 



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 like 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 I am unable at present to investigate this part of the vascular 

 system of Amiurus, I shall say nothing further in regard to them. 



THE UROGENITAL SYSTEM. 

 THE KIDNEY. 



The kidney has been carefully described in a number of Siluroids 

 by Hyrtl 1 . Although this organ in Amiurus agrees closely with 

 these — especially with that of Silurus 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 vertebrae. The bulk of the gland lies above 

 this bridge, filling the space between the transverse process oi the 



1 8itz. Weiner Akd. 1851. 



