310 CONTRIBUTIOXS TO NORTH AMERICAN ICHTHYOLOGY IV. 



certainly occur, but such are not necessarily "hybrids." [Salmo, the 

 Latin name of S. salar, originally from salio, to leap.) 



The following observations on the species of trout are taken, with 

 some slight abridgment and alteration, from Dr. Giinther's account of 

 this ftimily (Cat. Fish. Brit. Mus. vi) : 



There is no other group of fishes which offers so many difficn-lties to the ichthyol- 

 ogist, witli regard to the distinction of the species, as well as to certain points in 

 their life history, as this genus. * * * The almost infinite variations of these fishes 

 are dependent on ago, sex, and sexual development, food, and the properties of the 

 water. * * » The 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 the same kind of coloratiou. The young in all the species 

 of tills genus 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 Salmo alone, but also to 

 Thymallus and probably to Coregonus. The number of bars is not quite constant, but 

 the migratory trout have two (or even three) more than the river-trout. When the 

 Salmones have passed this " parr" state, the coloration becomes much diversified. The 

 males, especially during and immediately after the spawning time, are more in- 

 tensely colored and variegated than the females, specimens not mature retaining a 

 brighter silvery color, and being more similar to the female fish. Food appears to 

 have less influence on the coloration of the outer parts than on that of the flesh ; 

 thus, the more variegated specimens are frequently out of condition, whilst well-fed 

 individuals, with pinkish flesh, are of more uniform though bright colors. * » » 

 The water has a marked influence on the colors. Trout with intense ocellated spots 

 are generally found in clear, rapid rivers and in alpine pools ; in the large lakes, with 

 I)ebbly bottom, the fish are bright silvery, and the ocellated siiots are mixed with or 

 replaced by X-sli^'P'^fl^ black spots ; in dark holes, or lakes with peaty bottom, they 

 often assume an almost uniform blackish coloration. 



The brackish or salt water has the effect of giving them a bright-silvery coat, 

 without or with few spots, none of them ocellated. With regard to size, the various 

 species do not present an equal amount of variation. Size appears to depend on the 

 abundance of the food and the extent of the water. Thus, the migratory species 

 do not appear to vary considerably in size, because they find the same conditions in 

 all the localities inhabited by them. A widely-spread species, however, like Salmo 

 fario (or in America, Salmo purpuralus), when it inhabits a small mountain pool, with 

 scanty food, never attains a weight of H ounces, while in a largo lake or river, where 

 it finds an abundance of food, it attains to a weight of 14 or IG pwnids. Sucli large 

 river-trout are frequently named or described as Salmon-trout, Bull-trout, Steel-heads, 

 etc. 



The j)roportions of the various parts of the body to one another vary exceedingly, 

 in the same species, with age, sex, and condition. 



The fins vary to a certain degree. The variation in the number of rays in any one 

 genus (except Oneorhynchus) is inconsiderable, and of no value for specific distinction. 

 Although some species appear to be distinguished by a comparatively low dorsal and 

 anal fin, yet the proportion of the lieight of these fins to their length is a rather un- 

 certain character. In most of the species the fin-rays are longer during the stages of 

 growth or develoiiment. The caudal fin esjiecially undergoes changes with a<;e. 

 Young specimens of all species have this fin more or less deeply excised, so that the 

 young of a species which has the caudal emarginato throughout life is distin- 

 guished by a deeper incisiou of the fin from the young of a species which lias it 

 truncate in the young state. The individuals of the same species do not all attain 

 to maturity at the same size. 



