4 SALMOKID^. 



spots are generally found in clear, rapid rivers and in small, open, 

 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 pools or parts of lakes with muddy or 

 peaty bottom the Trout are of a darker colour generally, and when 

 enclosed in caves or holes they may assume an almost uniform 

 blackish coloration. The brackish or salt water has the effect of 

 giving them a bright-silvery coat, without or with comparatively 

 few spots, none of which are ocellated. JN^ow some of the species 

 like S. fario inhabit all the different waters indicated, even brackish 

 water, and therefore we find an immense variation of colour in one 

 and the same species ; others are more restricted in their habitat, 

 like S. solar, S. ferox, (fee, and therefore their coloration may be 

 more precisely defined. 



With regard to size the various species do not present an equal 

 amount of variation. Size appears to depend on the abundance of 

 food and the extent of the water. Thus, the Salmon and the dif- 

 ferent kinds of Great Lake -trout 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 /S^. fario, 

 when it inhabits a small mountain-pool with scanty food, never 

 exceeds a Aveight of eight ounces, while in a large lake or river where 

 it finds an abundance and variety of food it attains to a weight of 

 fourteen or sixteen pounds. Such large River -.trout are frequently 

 named and described as Salmon-trout, Bull-trout, &c. 



The proportions of the various parts of the body to one another vary 

 exceedingly in one and the same species. First of all, we find in 

 young Salmonoids the same peculiarities which characterize a young 

 fish generally (short snout, large eyes, cylindrical body, &c.), or in 

 mature ones those indicating the development of the sexual organs 

 (prominent abdomen, great depth of the body). But in scarcely any 

 other group of fishes do we observe a similar change in the form of 

 the snout. In the mature male the intermaxillaries and the mandible 

 are produced in various degrees, and the latter is frequently more or 

 less bent upwards. Hence the males have- the snout much more 

 pointed and produced, and the entire head longer, than the females ; 

 with the intermaxillary bone the teeth with which it is armed are 

 also enlarged, sometimes to four times the size of those of the females. 

 And if this development of the front part of the head happens to be 

 going on while the individual is able to obtain only a scanty supply of 

 food, the usual proportions of the head and trunk are so altered that 

 the species is very difiieult to recognize. Barren male fish approach 

 the females in the proportions of the head and body, but hybrid fishes 

 do not differ in this respect from their parents. The abundance or 

 scarcity of food, and the disposition or indisposition of the Salmonoids 

 to feed, are other causes affecting the growth or falness of the 

 various parts of the body. In weU-fed fishes the head is propor- 

 tionally not only smaller, but also shorter, and vice versd. 



The Jins vary to a certain degree. The variation in the number of 

 the rays is inconsiderable and of no value for specific distinction ; we 



