20 THE SEA-TROUT 



I have indicated that the migratory habits of certain fish have been 

 taken by lawyers as the test of their nature, and, further, that angUng 

 writers, in their writings, have at least been strongly influenced by these 

 habits. Indeed, no more strikingly marked feature of distinction would 

 probably occur to a superficial observer. But Mr. Regan, discussing 

 the trout, tells us that there " is sufficient evidence that the migratory 

 and non-migratory fish arc not distinct species, nor even races." It is 

 necessary to examine the evidence which Mr. Regan adduces in support 

 of this assertion ; and I think the reader will agree that the evidence, if 

 not conclusive, is at any rate extremely suggestive and interesting. I 

 shall take the various points in their order. 



I. — There are no Structural Differences between Sea-trout 

 AND Trout. 



I cannot believe that anv investigator would commit himself to so 

 sweeping a statement as this unless he had, from exact study of many 

 specimens, fully convinced himself of the fact. I am not competent 

 to dispute Mr. Regan's accuracv of observation, and, indeed, would 

 prefer to credit its correctness rather than attach weight to the numerous 

 alleged points of difference which other observers have professed to 

 discover in specimens submitted to them. 



Apart from superficial colouring (which is of course a structural 

 difference though on a microscopical scale), differences in the form of 

 the gill-covers, differences in the arrangement of the teeth, and 

 differences in the shape and size of the fins, have all been claimed at 

 different times as constituting typical and characteristic distinctions. 

 But even admitting these and similar points of difference to occur in 

 certain specimens with more or less frequency and constancy, it seems 

 to me possible to attach more weight to them than they deserve in the 

 discussion as to whether migratory and non-mieratory habits are 

 conclusive as to species — or even race. Until a marked structural 

 difference, constantly ocrurrine, is proved to exist, I think we must 



