266 A HISTORY OF FISHES 



the Cape of Good Hope, Southern Australia and New Zealand, 

 but one species from Patagonia, Australia, and New Zealand 

 reverses the habit of its northern relatives and returns to its 

 original home in the sea for purposes of reproduction. 



Anadromous fishes are also to be included among those which 

 spend a part of their life in the sea, for such fishes feed and grow 

 in this habitat, merely ascending the rivers at more or less 

 regular intervals to spawn. The best known examples of fishes 

 of this type are the Sea Lamprey {Petromyzon), Sturgeon {Aci- 

 penser), Shad (Alosa), Salmon, Trout (Salmo), and Char (6*^/- 

 velinus) . The memlDcrs of the Salmon family (Salmonidae) are 

 primarily marine fishes of arctic and northern seas, but include 

 a large number of species which have become permanently 

 established in the fresh waters of Europe, Northern Asia, and 

 North America. The various Salmon and Trout comprise 

 a genus {Salmo) represented by about ten species in the North 

 Atlantic and North Pacific: those from the Atlantic form a 

 natural group distinct from those of the Pacific, the latter being 

 placed by some authorities in a separate genus (Oncorhynchus). 

 Our own Salmon and Trout are to be regarded as two very 

 closely related species, each with roughly the same range in 

 the sea, and each entering the rivers to breed. They are found 

 in the sea from Iceland and the northern part of Norway 

 southwards to the Bay of Biscay, but whereas the Salmon 

 {S. salar) has succeeded in crossing the ocean and is found on 

 the Atlantic coast of North America, the Trout {S, trutta)^ which 

 normally does not go nearly so far out to sea, is absent from 

 America. In some of the larger lakes and rivers of Quebec, New 

 Brunswick, and Maine there are Salmon {Sebago and Ouananiche) 

 which never go to the sea, having become permanent residents 

 in fresh water. In Europe, where it occurs alongside the 

 Trout, the Salmon does not generally form fresh-water colonies 

 in this way, but Lake Wenern in Sweden, now completely 

 isolated from the sea by inaccessible falls, possesses a stock of 

 land-locked and non-migratory Salmon. The Trout forms 

 fresh-water colonies in practically every suitable lake and river 

 which it enters, and many of these permanent residents have 

 become so much modified in the course of time that they present 

 an extraordinary diversity of form, size, coloration, and so on, 

 some of the fresh-water races being so dififerent from their 

 migratory ancestors that they have been regarded as distinct 

 species. Indeed, it is difficult to believe that the lordly Trout 

 of a deep lake, scaling as much as fifty pounds, and the small 



