INTRODUCTORY 33 



As I have stated, the dispute, or rather discussion, is not very 

 material to the purpose, the more so if we accept Mr. Regan's account 

 of the manner in which our streams became peopled with trout, namely, 

 through their having been invaded from the sea by trout which were 

 de facto migratory, some of which gradually lost the extreme migratory 

 habit. Such acquiescence in Mr. Regan's account would also involve 

 acquiescence in the theory " that the migratory and non-migratory fish 

 are not distinct species, nor even races," unless it be maintained that the 

 invaders consisted of more than one species or race, or had since 

 diverged into such, in my opinion an improbable development. 



The reader who has been patient enough to follow the argument is 



as capable as I am of forming a judgment upon the problems which I 



have thus presented to him. But probably the first observation which 



occurs to him will be that, even accepting Mr. Regan's explanation of 



the original stocking of our waters with trout, he would like to have 



some clear proof that the interchange of habits and environment which 



Mr. Regan, predicates actually takes place in our waters to-day. It is 



no reflection upon the general soundness of Mr. Regan's position that 



he cannot furnish such proof as would convince a British jury, but I 



think the theory which he expounds — for one hardly ventures to accept 



it as fact — is worthy of the most respectful consideration. There can 



be no doubt of this at least that the migratory and non-migratory trout 



are sometimes so alike that cases often occur where it is practically 



impossible to say definitely whether a particular fish is a sea-trout or a 



trout. In such cases the fish quite conceivably may be a trout which 



has taken on the colour of a salt-water environment or a sea-trout which 



r 

 has found congenial quarters in fresh-water. 



The late Mr. H. Cholmondeley-Pennell, who, following Yarrell 

 and others, made the very most of " distinctions " in " The Angler- 

 Naturalist," said : — " The difference in colour between the two fish — the 

 one being silver and the other golden — is usually too obvious to admit 



