INTRODUCTORY 13 



works away at minute differences in detail which the morphologist is 

 apt to regard as relatively trivial. The whole outlook is different." 



Now it seems to me to be necessary, in the inquiry to which we have 

 addressed ourselves, namely, What is a sea-truul? to recognise that there 

 are, in fact, two schools holding such very divergent aims, because it 

 may quite conceivably be important that we should be able to distin- 

 guish at any time whether a particular writer is discussing a particular 

 specimen as a morphologist or as a systematist. 1 can readily 

 understand that a failure to recognise this distinction may have led to 

 a misunderstanding of a particular writer's views, and I think that if a 

 writer has not made it clear in what capacity at the moment he is 

 discussing any specimen of the Salmonidcs a certain confusion of 

 thought may have unwittingly been engendered in the minds of his 

 readers. 



It occurs to me, for example, that much of the uncertainty which 

 at present exists as to the identity of the " bull trout " with the sea- 

 trout — one party strongly contending for identity and another party as 

 strongly contending for variety — rests upon the point of view of the 

 disputant as a morphologist or a systematist. If the former, he will 

 consider the " bull trout " as a sea-trout and of interest as being of the 

 Salmonida ; if the latter, he will discover a marked distinction between 

 the two fish on the alleged ground that in mature specimens of the 

 sea-trout the tail is square whereas the " bull trout " has a tail so 

 (onvex in its margin that the fish has, in consequence, in certain 

 localities, been popularly designated the " round tail." The morpho- 

 logist will as^rce that the family Salmonidcc is an interesting study; but 

 the systematist, intent on cataloguing his " bull trout." will classify it. if 

 not as a separate " species " of the " genus " Salino. at least as the 

 " variety " eriox of the " .species " trulia. 



To take now another example of even greater pertinency to our 

 subject. Viewing the family Salmonida;, the morphologist will, for his 



