FISHES OF LAKE SUPERIOR. 327 



when found in more temperate regions, occurs there in clear mountain 

 rivers, sometimes very high above the level of the sea, near the limits 

 of perpetual snow, or in deep, cold lakes. That this family is adapt- 

 ed to the cold regions is most remarkably exemplified by the fact 

 that they all spawn late in the season, at the approach of autumn 

 or winter, when frost or snow has reduced the temperature of the 

 water in which they live nearly to its lowest natural point. The 

 embryos grow within the egg very slowly for about two months 

 before they are hatched ; while fecundated eggs of some other fami- 

 lies which spawn in spring and summer, give birth to young fishes a 

 few days after they are laid. The Salmonidge, on the contrary, are 

 born at an epoch when the waters are generally frozen up ; that is, 

 at a period when the maximum of temperature is at the bottom of the 

 water, where the eggs and young salmons remain among gravel, 

 surrounded by a medium which scarcely ever rises above thirty 

 or forty degrees. 



It is plain from these statements, and from what we know other- 

 wise of the habits of this family, that there is no one upon the globe 

 living under more uniform circumstances, and nevertheless the species 

 are exfternely diversified, and we find peculiar ones in all parts of 

 the world, where the family occurs at all. Thus we find, in Lake 

 Superior, species which do not exist in the course of the Mackenzie 

 or Saskatchawan, and vice versa, others in the Columbia river which 

 differ from those of the Lena, Obi, and Yenisei, while Europe again 

 has its peculiar forms. 



Whoever takes a philosophical view of the subject of Natural 

 History, and is familiar with the above stated facts, will now under- 

 stand why, notwithstanding the specific distinctions there are between 

 them, the trouts and whitefishes are so uniform all over* the globe. 

 It must be acknowledged that it is owing to the uniformity of the phys- 

 ical conditions in which they occur, and to which they are so admira- 

 bly adapted by their anatomical structure, as well as by their instinct. 

 Running up and down the rapid rivers and mountain currents, leaping 

 even over considerable waterfalls, they are provided with most pow- 

 erful and active muscles, their tail is strong and fleshy, and its broad 

 basis indicates that its power is concentrated ; it is like the paddle of 

 the Indian who propels his canoe over the same waters. Their 



