138 NORTHERN ZOOLOGY. 



that very minute observation and much practical skill are requisite for the due dis- 

 crimination of the species. No attempt that has hitherto been made to frame 

 proper specific characters for the trouts has succeeded, and a great number of 

 names have consequently been introduced into science which it is almost impos- 

 sible to appropriate correctly. In some instances, several nominal species have 

 been created, by the description of different states of the same trout under separate 

 names, and as frequently two or more species have been confounded together. 

 Most of the American trouts, though perfectly distinct, have been described as 

 identical with the common European ones. The rectification of this confusion is 

 a matter that concerns the legislator as well as the naturalist, for nothing certain 

 can be learnt of the habits of a trout until we have the means of recognising it in 

 its various stages of growth ; nor without such knowledge can the legislative enact- 

 ments which abound in North America, as well as in Europe, be of much utility, 

 or indeed fail of being actually injurious. Figures, unless perfectly correct in all 

 the details, do not aid us much in distinguishing species which are so similar in 

 external form ; and descriptions of colour, if unaccompanied by notices of peculia- 

 rities of structure, as is the case in many ichthyological works, are of still less ser- 

 vice. The hues and markings of the trouts are modified by their age, food, and 

 other circumstances. The younger individuals are generally more spotted than the 

 older ones, which have a more uniform and often a deeper colour. When a trout 

 has abundance of its proper aliment, as must be generally the case before it can 

 attain a spawning condition, its scales acquire a splendour, and its markings an 

 intensity and distinctness very different from what the same fish exhibits when out 

 of season — so that we might say with M. Agassiz, these fish bedeck themselves, like 

 birds, in a nuptial garb. This gentleman also observes, that the tints of the trouts 

 are most brilliant, and their colours most vivid in the autumn, and at the time of 

 the greatest cold, or in the months of October, November, December, and January ; 

 which is the precise period of the development of the spawn in many of the species. 

 He likewise states that the most beautiful Salmon-trout are found in waters which 

 abound in small Crustacea, direct experiments having shown to his satisfaction 

 that the intensity of the red colour of their flesh depends upon the quantity of 

 gammarince which they had devoured. Dr. Knox's researches give a nearly 

 similar result, by proving the red substance which is generally to be found in the 

 intestines of a salmon that has recently quitted the sea to consist of the eggs of 

 echinodermata and Crustacea. To this rich aliment he attributes the brilliancy of 

 the scales of a salmon in prime condition, and the high flavour and deep colour 

 of its flesh. 



