470 Dr KNOX on the Natural History of 



experiments to prove that he feeds on this kind of food, every re- 

 corded fact proves the very reverse : they become at last disagree- 

 able objects to look at ; I have opened the stomach of a fish 

 killed by the poacher in the month of October, nearly 100 miles 

 from the ocean, with the peculiar food and none else, still in the 

 intestines, and this in probably the finest trouting stream in 

 Scotland, and of course full of trout food, which, in this extended 

 run, occupying at the least several days, he had altogether de-r 

 clined touching. These important facts seem to me to determine 

 the following points : the true and only feeding ground, which 

 is strictly the ocean ; the breeding ground, which is the fresh 

 water stream, whether principal or tributary. The part of the 

 river influenced by the tide is a kind of debateable ground in 

 which he neither feeds nor breeds, but which a few enter with 

 the tide, or during great floods of the river, seemingly because it 

 lies within their ultimate range of migration. Of the causes 

 which may induce the true salmon to take to rivers besides the 

 great and avowed one, the propagation of his species, there may 

 be others difficult to understand. The facts which I have collect- 

 ed on this point are not many, but by being recorded, they may 

 serve as a nucleus to others ; they tend to shew that those parasi- 

 tical animals which prey on him whilst in salt water, as the Mo- 

 noculus piscinus, which adheres to the integuments, and the tape- 

 worm * which generally fills the pancreatic cceca, are disposed 

 to leave him, and probably do entirely quit, during his residence 

 in fresh water : the fact is beyond dispute with regard to the first 

 of these parasitical animals, but is unimportant when compared 

 with the history of the tape-worm, whose continued presence, 

 growth, and reproduction, must ultimately, unless checked by 

 some wise provision in Nature, prove his destruction as it does in, 



* Mr RUDOLPHI arranges this kind of tape worm with the " Botriocephali.'" His 

 authority in this respect I should suppose to be superior to every other. 



