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Show 1870.] IN THE GROWTH OF SALMON. 39 Dr. Gunther himself professes to have been sceptical concerning hybrid Salmonoids under natural conditions, until convinced, through the Rev. Augustus Morgan, of a cross between the Sewin (S. cambri-cus) and the River-trout (S. fario)*. It is said " These hybrids are so numerous in the Rhymney and other rivers of South Wales, and so variable in their characters, that the passage from one species to the other may be demonstrated in an almost unbroken series, which might induce some naturalists to regard both species as identical." They retain the migratory impulse seawards, and are sexually developed in the autumn,-when young, are like Trout-when older, Sewin. On their first ascent from the sea they are slightly smaller, but closely resemble Sewin. On their second migratory return they are darker and redder than either supposed parent. These equivocal hybrids, W . Peel, Esq., of Taliaris Park, retained for years in a freshwater pond, where they grew from 15 to 18 inches long, but remained sterile. Males preponderate. It is not stated precisely on what evidence these fishes claim hybridity, more than that they bear resemblances to both species. Indeed, from Dr. Giinther's own descriptions, the Sewin characters preponderate. If, therefore, Siebold's observations, checked by Widegren's subsequent data (viz. that some individuals of every Salmonoid species are very late in being sexually developed, or have as it were a longer temporary immaturity, and during such period differ from those normally developed), be applied to this instance of hybridism, it may on such grounds be maintained that the said hybrids are after all nothing but retarded examples of S. cambricus. Taken in this light, these so-called hybrids offer coincident analogies to the retarded conditions assumed to occur in S. salar, and notably in those two specimens which have formed the basis of the present paper. It seems to me also a legitimate inference that the two fishes reared in our aquarium are Salmon, inasmuch as they differ in a far greater degree from all other European species than from S. salar. Indeed, as is broadly admitted in the British-Museum Catalogue, p. 3, of the genus Salmo, " The almost infinite variations of these fishes are dependent on age, sex and sexual development, food, and the properties of the water ;" hence this very same reasoning which demonstrates peculiarities in the two Salmonoids and brood in question, logically points to their immaturity, retardation, or masking of the normal adult characters of the species. If their entire growth has been prejudicially influenced by continuous retention in fresh water, so may a defect or abnormal number of scales (two transversely) and pyloric appendages (three or four) be but the concomitant effect of unnatural development. Suppose, again, our oft-quoted Garden specimens were a cross breed between any two well-known species, freshwater or marine, there remains still a wide loophole of doubt why they have remained so very small-sized. No European species whatever, to m y know- * See B. M. Cat. of Fishes, vol. vi. p. 8. |