'PLASTICITY' OF SALMONID^. 17 



'Plasticity' of Salmonid^. 



The marine Salmonidse ascend rivers to breed. The fresh-water salmonids breed in 

 the lakes and streams. In certain instances fresh-water Salmonidae descend to the sea 

 presumably to feed, but the strictly marine forms do not interbreed to any appreciable 

 extent with fresh-water forms. In the extreme north the salmonids are almost exclu- 

 sively marine. In the extreme southern distribution they are exclusively fresh-water, 

 or inland forms. Each of various inland water basins possesses forms which differ more 

 or less from those of other inland water basins, and from those which ascend fresh-water 

 streams from the sea principally to breed. 



As previously mentioned, some ichthyologists have regarded each of these differing 

 forms as distinct species, while others have pronounced all forms comprised in one 

 genus a single species and ascribe the differences to 'plasticity.' This use of the term 

 seems to signify that the fish is 'as clay in the hands of the potter,' the potter being 

 environment, and if the clay is transferred to the hands of a different potter, it is moulded 

 accordingly. 



It is manifestly impossible to transfer all individuals of one basin to another. A few 

 so transplanted would be another restrictive isolation, and such a group, if it survived, 

 and maintained its integrity, would in time differ from that of the stock from which it 

 was separated, regardless of any difference of environment. So 'plasticity' of segregated 

 forms is only another name for limited interbreeding or 'close breeding.' 



THE ATLANTIC SALMON {SALMO SALAR LINNE). 



Plates 1-4- 

 General Considerations. 



Based upon Systema Naturce of Linnaeus, 1758, as determined by rules of zoological 

 nomenclature and general usage, Salmo solar has been designated as the type of the 

 family Salmonidse. 



There are very few other fishes having any vernacular name at all that have the 

 distinction of being everywhere known to the EngUsh-speaking peoples by one name 

 only. Everywhere it is 'the Salmon.' Sometimes there are local names for the two 

 sexes, the different stages of growth, or physical condition; or the names of the rivers in 

 which it is caught are added as prefixes, but at the same time it is recognized as salmon. 

 In each foreign language, too, there is one name for the fish, which forms the basis for 

 the names of other salmonids. As in EngUsh there is the 'salmon trout,' so other tongues 

 have hke names to distinguish the trouts and at the same time indicating a relationship. 

 There are many of such recognized forms and combination names for them, but only 

 one sahnon. In most regions the other closely related forms are trout or the equivalent 

 for trout in whatever language, though occasionally a trout with some qualifying word 

 is called salmon, as the Swedish name for the sea trout which translated is 'gray salmon.' 



