108 SALMONIDJ:. 



principal argument being this, that he has caught small fish, 

 no longer than the finger, with a fly, " which had as perfect a 

 hard stomach as the larger ones, with the coats as thick in 

 proportion, and the same shells within." 



In external appearance, the Gillaroo is said to differ from the 

 Common Trout " very little, except that they have more red 

 spots, and a yellow or golden-coloured belly and fins, and are 

 generally a broader and thicker fish." Again, Sir Humphrey 

 admits that, " in a clear and cool river, fish that feed much on 

 larvse, and swallow the hard cases, become yellower, and the 

 red spots increase so as to outnumber the black ones ; and these 

 qualities become fixed in the young fishes, and estabKsh a 

 particular variety." 



This would seem, in plain English, to describe the existence 

 of a fish in the direct process of change, from the ordinary form 

 of the Trout to the Gillaroo, the feeding on the larvse of winged 

 insects, in their hard stony cases, being, as it were, a first step 

 toward becoming shell-fish eaters, and the effect being indicated 

 in the gradual change of colour, though the causes have not 

 been as yet sufficiently powerful to produce the induration of 

 the stomach. 



In America, likewise, it has been attempted to draw a dis- 

 tinction ; and Dr. Dekay, a very accomplished and able icthy- 

 ologist, although perhaps — with all deference be it spoken — 

 rather too much of an in-door naturalist, and too much inclined 

 to admit hearsay evidence, has designated a species as the Hed- 

 bellied Trout {Salmo Erythrogastei') ; which I confess I do not 

 believe to be even a permanent variety, but merely a brilliant 

 specimen of the common Brook Trout, in its highest season. 



