I II. AD-KIDNEY IN ADULT TELEOSTEANS AND GANOIDS. 849 



which I shall in future call lymphatic tissue. Thus tJiejwhole 

 of that part of the apparent kidney in front of the ureter, including 

 the whole of the so-called head-kidney, is simply a great mass of 

 lympJiatic tissue, and does not contain a single urinifcrous tubule 

 or Malpigldan body. 



The difference in structure between the anterior and posterior 

 parts of the so-called kidney, although not alluded to in most 

 modern works on the kidneys, appears to have been known to 

 Stannius, at least I so interpret a note of his in the second edi- 

 tion of his Comparative Anatomy, p. 263, where he describes the 

 kidney of the Sturgeon as being composed of two separate parts, 

 viz. a spongy vascular substance (no doubt the so-called head- 

 kidney) and a true secretory substance. 



After arriving at the above results with reference . to the 

 Sturgeon I proceeded to the examination of the structure of the 

 so-called head-kidney in Teleostei. 



I have as yet only examined four forms, viz. the Pike (Esox 

 Indus), the Smelt (Osmerus eperlanus], the Eel (Anguilla an- 

 guilld], and the Angler (LopJiius piscatorius). 



The external features of the apparent kidney of the Pike 

 have been accurately described by Hyrtl 1 . He says: "The 

 kidneys extend from the second trunk vertebra to the end of 

 the abdominal cavity. Their anterior extremities, which have 

 the form of transversely placed coffee beans, are united together, 

 and lie on the anterior end of the swimming bladder. The con- 

 tinuation of the kidney backwards forms two small bands, sepa- 

 rated from each other by the whole breadth of the vertebral 

 column. They gradually, however, increase in breadth, so that 

 about the middle of the vertebral column they unite together 

 and form a single symmetrical, keel-shaped body," &c. 



The Pike I examined was a large specimen of about 58 

 centimetres in length, and with an apparent kidney of about 25^ 

 centimetres. The relations of lymphatic tissue and kidney 

 tissue were much as in the Sturgeon. The whole of the ante- 

 rior swelling, forming the so-called head-kidney, together with 

 a considerable portion of the part immediately behind, forming 

 not far short of half the whole length of the apparent kidney, 



1 "Das UropoctUche System der Knochenfische," .v/':. <l. /r/V//. Aka<l., isuo. 



