FISHES. 



Kil 



differences are very trivial in kind, and not gi-cater tlian would be expected on llie 

 h3'pothesis of recent ada])tation to lake-life. We have, therefore, on our Atlantic 

 coast but one species of salmon, Salmo salar. Dr. Francis Day, who has very thor- 

 oughly studied these fishes, takes, in his Memoir on the Fishes of Great Britain and 

 Ireland, and in other papers, a similar view in regard to the European species. 

 Omitting the species with jiermanent teeth on the shaft of the vomer (sub-genus 

 Salar) he finds among the salmon proper but two S25ecies, Salmo salar and Salmo 

 trutta. 



The latter species, the sea-trout or salmon-trout of England, (Fig. 99) is similar to 

 the salmon in many respects, but has rather smaller scales, there being 14 in an oblique 

 series between the adipose fin and the lateral line. It is not so strong a fish as the 

 salmon, nor tloes it reach as large a size. Although naturally anadromous, like the 

 salmon, land-locked forms are not uncommon. These have Ijeen usually regarded as 

 different species, while aberrant or intermediate individuals are usually regarded as 

 hybrids. 



The present writer has examined many thousands of American Salmonidfe, both of 

 Oncorhtjnchus and Salmo. While many variations have come to his attention, and he 

 has been compelled more than once to modify his views as to specific distinctions, he 

 has never yet seen an individual which lie had the slightest reason to regard as a 

 'hybrid.' It is evident that in America but few species of Salmonoids exist, and that 

 these are subject to many variations. It is certainly illogical to conclude that every 

 specimen which does not correspond to our closet-formed definition of its species must, 

 therefore, be a hybrid with some other. There is no evidence worth mentioning, 

 known to me, of extensive hybridization in a state of nature in any group of fishes. This 

 matter is much in need of further investigation, for what is true of the species in one 

 region, in this regard, may not be true of others. The sjiecies of trout, also, may jjer- 

 haps hybridize, while Salmo salar and the Oncorhynchi do not. 



Dr. Giintlier observes: "Johnson, a correspondent of Willughby, had already 

 expressed his belief that the different Salmonoids interbreed ; and this view has since 

 been shared by many who have observed these fishes in nature. Hybrids between the 

 sewin {Salmo trutta xm-.cambricus) and the river trout {Salmo fario) were numerous 

 in the Rhymney and other rivers of South Wales, before Salmonoids were almost 

 exterminated by the pollutions allowed to pass into those streams, and so variable in 

 their characters, that the passage from one species to the other could be demonstrated 

 in an almost unbroken series, which might induce some naturalists to regard both 

 species as identical. Abundant evidence of a similar character has accumulated, 

 showing the frequent occurrence of hybrids between Salmo fario and S. trutta. . . . 

 In some rivers the conditions appear to be more favorable to hybridism than in others, 

 in which hybrids are of comparatively rare occurrence. Hybrids between the salmon 

 and other species are very scarce everywhere." 



The black-spotted trout, forming the sub-genus Salar, differ from Salmo salar 

 and Salmo trutta in the greater development of the vomerine teeth, which are 

 persistent throughout life, in a long double series on the shaft of the vomer. About 

 seven species are laboriously distinguished by Dr. Gunthei-, in the waters of western 

 Europe. Most of these are regarded by Dr. Day as varieties of Salmo fario. The 

 latter species, the common river-trout or lake-trout of Europe, is found throughout 

 northern and central Europe, wherever suitable waters occur. It is abundant, gamey, 

 takes the hook readily, and is excellent as fpod. It is more hardy than the different 



VOL. III. — 11 



