484 Bulletin 47, United States National Museum. 



closely related, and difficult to distinguish, if indeed all be not necessarily 

 regarded as forms of a single one. The excessive variations in color and 

 form have given rise to a host of nominal species.* (Salmo, the Latin 

 name of Salmo solar, originally from salio, to leap.) 



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

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

 family. (Cat. Fish. Brit. Mus., vi, 3-5, 1866): 



There is no other 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 

 almost infinite variations of these fishes are dependent on age, 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 coloration. The 

 young in all the species of this 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 intensely 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 pebbly bottom, the fish are 

 bright silvery, and the ocellated spots are mixed with or replaced by 

 X-shaped 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 upon the abundance of the food and 

 the extent of the water. Thus, the migratory species do rot 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 mykiss'], when it inhabits a small moun- 

 tain pool, with scanty food, never attains a weight of 8 ounces, while in 

 a large lake or river, where it finds an abundance of food, it attains to a 



* European writers have described numerous hybrids among the various species of Salmo, real 

 and nominal, found in their waters ; as also among the various European Cyprinidse. We have 

 thus far failed to find the slightest evidence of any hybridism either among our American 

 Scdmonidee or Oyprinidse, in a state of nature. Puzzling aberrant or intermediate specimens 

 certainly occur, but such are not necessarily "hybrids." 



