SALMONIDJE. 87 



with them, when once pointed out, cannot be readily mistaken, and, 

 being both permanent and invariable, are quite sufficient to establish 

 diversity of species. 



It is not in formation, moreover, or appearance only, but in very 

 many of its habits, that the Brook Trout, Salmo Fontinalis, of Ame- 

 rica, differs from his congener, the common Trout, Salmo Fario, of 

 Europe. 



Still, in general, his manners, his haunts, his prey, and his mode of 

 taking it, so closely resemble those of the European Trout, that as a 

 general rule, the instructions given for the taking the one will be found 

 successful as regards the other ; and the flies, baits, and general style 

 of tackle, as well as the science of capturing, with some few excep- 

 tions, which will be noticed hereafter, are nearly identical, on the 

 two sides of the Atlantic. As in Europe, so in America, although 

 there are countless varieties of this most beautiful of fishes, almost 

 indeed a variety for every stream, still, according to the opinions of 

 what I deem the best authorities, there is but one distinct species. 



Endless attempts have been made in England to distinguish and 

 define fresh species ; but these have, in my judgment, all failed. 

 According to Mr. Agassiz, whose opinion on this subject I consider 

 paramount to all others, the Gillaroo, or Gizzard-trout, as it is some- 

 times erroneously called by the Irish, and some of the Scottish writers, 

 is merely a casual variety of the Salmo Fario. The distinction, which 

 consists principally in the thickness and induration of the stomach, 

 having arisen from feeding on shell-fish, in the first instance, in indi- 

 viduals, has been gradually ingrf fted on generations, until, in process 

 of time, it has become a permanent type. 



Although this variety is not known to exist on this continent, I have 

 a very strong suspicion, from many circumstances which I have heard, 

 on good authority, concerning the Trout of the Marshpee river, in Mas- 

 sachusets, that on examination, it will be found to possess some of the 

 leading peculiarities of this fish, particularly the indurated stomach. 

 I have never had an opportunity of seeing the Trout of this river ; 

 but I know that it has many peculiarities of habit resembling those of 

 the Gillaroo, especially that of feeding on shell -fish, a friend of mine 

 having actually succeeded in taking them with small white crabs, at a 

 time when they would look at no other bait. 



