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Show 1884.] HYBRIDS A M O N G T H E SALMONIDcE. 35 Dr.Giinther. Non-rnigratory forms. Salmo levenensis ,, 49-90. » ,, fario,var. gaimardi „ 33-46. i, „ var. aworm... „ 38-47. „ ferox „ 43-49. „ „ stomachicus „ 44. ,, ,, gallivensis „ 44. ,, „ nigripinnis „ 36-42. Mr. Day. Non-migratory forms. Salmo fario:- Gloucestershire Caec. appen. 34-39. Cornwall & Cardiganshire ,, 35-44. Yorkshire „ 35. Sutherlandshire „ 46, ,, ,, Salmo levenensis:- At Howietoun ,, 47. ., „ 4 S. salar & S. levenensis „ -j ' _^' „ Migratory form 2 S. salar, Devonshire... „ 61,71. Mr. Arthur. Non-migratory form Salmo fario, var ausonii, „ 43-54. New Zealand. I do not propose referring to the foregoing, as I have elsewhere (British and Irish Fishes) entered on a consideration of how the Brook-Trout, transported to a warmer climate, and where food is abundant, has taken on a structural change, conclusively showing that the number of cseca is not invariable, but changes with changing circumstances, and consequently cannot be a criterion of species ; for all the eggs of the Brook-Trout sent to Tasmania were from districts considered by Dr. Giinther to be inhabited by the race ausonii of Salmo fario, in which he had found from 38 to 47 caecal appendages only : the same result of change being likewise shown in the transference of Lochleven Trout to Howietoun. I do not propose arguing upon the foregoing premises, but they may tend to prove that in undoubted hybrids the percentage hatched is comparatively small, that the number of malformations is great, and the young appear to be sickly. On the other hand, it does not seem unreasonable to almost doubt whether there exists specific difference between the American and British Charrs, monstrosities being rare, and the young strong. The sole male Charr employed had been some time ready for spawning before being used, and doubts were expressed at the condition of the milt. After one or two years' more enquiry, a trustworthy answer may be given ; but so far as hybrids from Howietoun have gone, sterility appears to be the rule, as yet no exceptions having been noticed, but the examples have been few. Much stress has been laid upon the number of finger-marks or transverse bars along the sides of various forms of Salmonidae, as characteristic of species. Thus in the second edition of the Parr Controversy (1883) we are told (p. 126) that in the Salmon there are nine or ten', but in the Trout only six or seven; while those of the Charr are not alluded to. Dr. Giinther, in his ' Introduction to the Study of Fish,' repeats the popular idea when he observes, " T h e number of bars is not quite constant, but the migratory Trout have 2 Tand even 3) more than the River-Trout" (p. 631). v 3* |