HEAD-KIDNEY IN ADULT TELEOSTEANS AND GANOIDS. 851 



Each of these bodies forms a compact oval mass, with the 

 ureter springing from its hinder extremity, situated in a forward 

 position in the body-cavity. Sections through the kidneys 

 shewed that they were throughout penetrated by uriniferous 

 tubules, but owing to the bad state of preservation of my speci- 

 mens I could not come to a decision as to the presence of 

 Malpighian bodies. The uriniferous tubules were embedded in 

 lymphatic tissue, similar to that which forms the anterior part of 

 the apparent kidneys in other Teleostean types. 



With reference to the structure of the Teleostean kidneys, 

 the account given by Stannius is decidedly more correct than 

 that of most subsequent writers. In the note already quoted he 

 gives it as his opinion that there is a division of the kidney into 

 the same two parts as in the Sturgeon, viz. into a spongy 

 vascular part and a true secreting part ; and on a subsequent 

 page he points out the absence or poverty of the uriniferous 

 tubules in the anterior part of the kidney in many of our native 

 Fishes. 



Prior to the discovery that the larvae of Teleosteans and 

 Ganoids were provided with two very distinct excretory organs, 

 viz. a pronephros or head-kidney, and a mesonephros or Wolf- 

 fian body, which are usually separated from each other by a 

 more or less considerable interval, it was a matter of no very 

 great importance to know whether the anterior part of the so- 

 called kidney was a true excretory organ. In the present state 

 of our knowledge the question is, however, one of considerable 

 interest. 



In the Cyclostomata and Amphibia the pronephros is a 

 purely larval organ, which either disappears or ceases to be 

 functionally active in the adult state. 



Rosenberg, to whom the earliest satisfactory investigations 

 on the development of the Teleostean pronephros are due, stated 

 that he had traced in the Pike (Esox Indus} the larval organ into 

 the adult part of the kidney, called by Hyrtl the pronephros ; 

 and subsequent investigators have usually assumed that the so- 

 called head-kidney of adult Teleosteans and Ganoids is the 

 persisting larval pronephros. 



We have already seen that Rosenberg was entirely mistaken 

 on this point, in that the so-called head-kidney of the adult is 



