28 THE SEA-TROUT 



6. — There is good reason to believe that in Nature the ranks of 

 THE Sea-trout are reinforced by the off-spring of the 

 River-trout and vice-versa. 



The previous passage suggests how the ranks of the sea-trout may 

 be reinforced " by the off-spring of the River-trout," and, subsequently, 

 throughout my account of the life-history of the fish, it will be seen how 

 at nearly every stage the influence of the sea-trout — not to put it any 

 more strongly — dominates the trout. 



It remains now to examine how the ranks of the trout may be 

 reinforced by the off-spring of the sea-trout, which is a deeper and more 

 wide-reaching question. It is so deep, indeed, that I do not think its 

 depths will soon be plumbed, but the theories to which the question has 

 given rise have occasioned much instructive speculation. 



Mr. Regan, then, asks us to consider the distribution of the trout. 

 " There are," he writes, " no true fresh-water fishes — Roach, Perch, 

 etc., — in the Hebrides, Orkneys, or Shetlands; yet in these islands 

 every river and loch is full of Brown Trout, which is only to be 

 explained by the supposition that the latter have been derived from the 

 Sea-trout, which have lost their migratory instinct in different places 

 and at different times." In other words, Mr. Regan's view is that the 

 trout is a sea-trout; not that the sea-trout is a trout. He ascribes to 

 the trout, in fact, a marine origin. 



Now it seems fairly certain that in order to arrive at the origin of 

 any species we must travel back a considerable distance, possibly 

 through aeons of evolution, into the dim and distant past. To establish 

 his point, however, Mr. Regan does not go so far back as that, but, 

 taking it for granted that trout then existed in the shape we know them 

 to-day, he carries us back to the Glacial Epoch. 



" It would be out of place here," he writes, " to enter into the causes 

 of this climatic change, but it seems clear that at a comparatively recent 

 date the whole of Northern Europe, including our islands except the 



