14 F. M. BALFOUR. 



find no tubules in the lymphatic tissue^ and in all cases the 

 number of them beyond the region of the well-developed part of 

 the kidney was so slight, that there can be little doubt that they 

 are functionless remnants of the anterior part of the larval kidney. 

 Their continuation into the anterior swelling, when present, con- 

 sisted of a single tube only. 



In the Eeel {Anguilla anguilla), which, however, I have not 

 examined with the same care as the Smelt, the true excretory 

 part of the kidney appears to be confined to the posterior portion, 

 and to the portion immediately in front of the anus, the whole 

 of the anterior part of each apparent kidney, which is not 

 swollen in front, being composed of lymphatic tissue. 



Loplims plscatorlus is one of the forms wliich, according to 

 Hyrti,! is provided with a head-kidney only, i. e. with that part 

 of the kidney which corresponds with the anterior swelling of 

 the kidney of other types. For this reason I was particularly 

 anxious to investigate the structure of its kidneys. 



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

 ureter springing from its hinder extremity, situated in a for- 

 ward position in the body cavity. Sections through the kidneys 

 showed 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 Mal- 

 pighiau 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 Wolffian 

 body, which are usually separated from each other by a more or 

 less considerable interval, it was a matter of no very great im- 

 portance 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 



1 " Das TJropoetische System de Knocheufische," ' Sitz. d. Wien. Akad.' 

 1850. 



