2870 THE BONY FISHES AND GANOIDS 



Having the dorsal nearly or quite opposite the pelvic fins, the mem- 

 lp bers of the typical genus Salmo are characterized by the small size of 

 the scales of the body, the strong and fully-developed teeth, and the presence of not 

 more than fourteen rays in the anal fin, and of numerous blind appendages to the 

 intestine. The cleft of the mouth is always deep, the maxilla extending up to or 

 beyond the line of the eye. Conical teeth are present not only in the margins of 

 the jaws, but likewise on the vomer and palatine bones, as well as on the tongue, 

 although there are none on the pterygoids. The eggs are remarkable for their 

 relatively large size; and the young, like those of most or all the other genera, are 

 marked with dark crossbars. In the males the lower jaw is more developed than 

 in the females, and at certain seasons may be developed into an upturned hook. 

 The genus is confined to the colder portions of the Northern Hemisphere, its 

 southern limits in the Old World being the rivers of the Hindu Kush and the Atlas 

 range, and in America the rivers flowing into the head of the Gulf of California. 

 Few zoological subjects have given rise to a greater amount of discussion than 

 the life history of the members of this genus, and the number of species by which it 

 is represented. As regards the latter point, great difference of opinion still prevails 

 among experts. Thus, for instance, Day considered that all the indigenous British 

 salmonoids might be arranged under three specific types, namely, the salmon, the 

 trout, and the charr; while other authorities admit an almost endless amount of 

 species. The subject is not one which admits of discussion in this work; and we 

 shall accordingly confine our notice to the salmon, the typical sea and river trout, 

 and the charr. As regards the variability of these fishes we may, however, quote 

 a passage from Dr. Giinther, who writes that "these are dependent on age, sex, 

 and sexual development, food, and the properties of the water. Some of the 

 species interbreed, and the hybrids mix again with one of the parent species, thus 

 producing an offspring more or less similar to the pure breed. The coloration is, 

 first of all, subject to variation; and consequently this characteristic 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 characteristic, not being peculiar to Salmo alone, but also common 

 to Thymallus, and probably to Coregonus. The number of bars is not quite con- 

 stant, but the migratory trout have two (and even three) more than the river trout. 

 In some waters river trout remain small, and frequently retain the parr marks all 

 their lifetime; at certain seasons a new coat of scales overlays the parr marks, 

 rendering them invisible for a time. When the salmonoids have passed this ' parr ' 

 state, the coloration becomes much more diversified. The males, especially during 

 and immediately after the spawning time, are more intensely colored and variegated 

 than the females; specimens which have not attained to maturity retaining a 

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

 have much less influence on the coloration of the outer parts than on that of the 

 flesh; the more variegated specimens being frequently out of condition, while well- 

 fed individuals with pinkish flesh are of a more uniform, though bright, coloration. 

 . . . The water has a marked influence on the colors; trout with intense ocel- 



