XVII. 



SPECIES OR VARIETIES IN OUR 

 SALMONIDAE. 



THERE is a well known and marked divergence 

 of view as to whether the various forms of our 

 Salmonidae are to be regarded as merely local 

 races and varieties, or as entitled to specific 

 rank. This difference of opinion appears to be 

 attributable to two main causes. One of these 

 is the extraordinary plasticity of the whole 

 family, as exemplified so strikingly in our 

 ordinary brown trout, which are found in every 

 variety of colour and marking ; dark trout and 

 light trout ; greenish trout and brown trout ; 

 some with large red spots and some with many 

 small spots ; others again with none, and so on 

 through an infinite variety of form. The other 

 main source of difference arises from the loose 

 and inaccurate use of the term 'species.' These 

 questions have been partially examined in my 

 previous chapter on the so-called ' Ferox.' It 

 is sufficient here to say that in the further con- 

 sideration of the relationship and differentiation 



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