The Natural History of the Salmon. 53 



of his remarks apply to the trout as well as the 

 salmon, they are, with his permission, introduced 

 here : 



" We know of no group of fishes which offers so 

 many difficulties to the ichthyologist with regard 

 to the distinction of the species, as well as to certain 

 points in their life history, as this genus (the sal- 

 monidae), although this may be partly due to the 

 unusual attention which has been given to their 

 study, and which has revealed an almost greater 

 amount of unexplained facts, than of satisfactory 

 solutions of the questions raised. The almost infi- 

 nite variations of these fishes are dependent on age, 

 sex and sexual development, food, and the pro- 

 perties of the water. Some of the species inter- 

 breed, and the hybrids mix again with one of the 

 parent species, thus producing an offspring more or 

 less similar to the pure breed. 



" TJte coloration is, first of all, subject to variation ; 

 and consequently this character but rarely assists in 

 distinguishing a species, there being not one which 

 would show in all stages of development the same 

 kind of coloration. The young of all the species 

 are barred, and this is so constantly the case that it 

 may be used as a generic or even as a family 

 character, not being peculiar to the Salmo alone, 

 but also to Thymallus and probably to Coregonus. 

 The number of bars is not quite constant, but the 



