36 RESULTS OF THE ATTEMPTS TO ACCLIMATISE SALMO SALAR. 



monger, we ascertain tliat in nine cases out of ten the silvery 

 form, the colour of the flesh, and the size alone determine 

 their opinion, and all such forms are pronounced and sold as 

 Salmo salar. All doubts of the classifier regarding the nicer 

 points are readily set aside as the trivialities of naturalists, 

 with perhaps the contemptuous observation " that no two 

 men of science are able to agree with each other's views in a 

 matter of classification." 



As regards the fish market it may be practically ascertained 

 that there are only three forms of the salmon family re- 

 cognised, viz.: (1) The common river or lake trout. (2) 

 The smaller sizes of migratory species, generally recognised 

 either as grilse or salmon trout. (3) All the large-sized 

 migratory forms, almost invariably recognised as salmon, i.e., 

 Sahno salar. 



In some cases the brown shade or colour, and number* 

 colour, or disposition of spots, may cause ordinary persons to 

 allow the possibility of hybridism ; but this admission is 

 rarely made in respect of characters which escai>e their 

 observation — sxich as the length of the maxillary, the develop- 

 ment of the limb of the prse-operculum, and the number and 

 size of the transverse series of scales. Nor is this to be 

 wondered at. As regards the genus Salvio, nearly all the 

 characters selected by the classifier are of the most unsatis- 

 factory nature. No two individuals agree in any point 

 exactly ; every selected character varies in the widest manner, 

 and the greater number of these overlap the bounds which 

 ideally sepai-ate the various species of the classifier. 



So long as the limits of variability of individuals of the 

 same parents in freedom are uncertain or obscure, reliance 

 upon the minute differences of many trivial characters must 

 certainly be a fertile source of error. Even observations 

 made in respect of fish in artificial confinement show that 

 within such restricted conditions individual variation is very 

 considerable. But this is a small matter. What naturalist 

 is prepared to declare the full extent of the limits of 

 individual variation as regards form, colour, and oruamenta- 

 tiou throughout the whole life development ah ovnvi, imder 

 all the possible changes of environment, including differences 

 in food, temperature, and otlier important conditions charac- 

 teristic of the different localities open to the migration of 

 fishes? It does not follow because we are unable satisfac- 

 torily to view the free movements of fish throughout their 

 life "history in difEcrent localities, as in terrestrial forms of 

 life, that "the changing conditions of environment do not 

 equally produce marked differences in many of the characters 

 now depended upon for the distinction of species. 



So long as individual variation, together with the iuflucuco 



