FISHES. 



161 



differences are very trivial in kind, and not greater than would be expected on the 

 hypothesis of recent adaptation to lake-life. We have, therefore, on our Atlantic 

 coast but one species of salmon, Salmo solar. 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 permanent teeth on the shaft of the vomer (sub-genus 

 Solar) he finds among the salmon proper but two species, 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 does it reach as large a size. Although naturally anadromous, like the 

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

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

 hybrids. 



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

 Oncorhynchus 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 he 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 mucli in need of further investigation, for what is true of the sj)ecies in one 

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

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



Dr. Gtinther 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 var. cambricios) 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 occui-rence. 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. Glinther, in the waters of western 

 Europe. Most of these are regarded by Dr. Day as varieties of Salm.o 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 food. It is more hardy than the different 

 VOL. HI. — 11 



