THE SALMON FAMILY 181 



migratory trout are coloured, spotted, and barred exactly like 

 the young of lake and river trout, and in shape they are so 

 closely similar as to require a long apprenticeship to enable one 

 to tell them apart. Even experts cannot always agree about 

 the species of these finger-marked salmonoids ; in fact, the 

 evidence about " orange-fins " of the Tweed, known as " yellow- 

 fins" in the Solway rivers, is so conflicting that magistrates have 

 refused repeatedly to punish persons convicted of killing them. 

 Some witnesses declare them to be the young of migratory 

 trout ; others pronounce them with equal confidence to be the 

 young of river-trout ; while those of a third school are ready 

 to swear that they are a distinct adult species. 



The juvenile dark bars, finger-marks, or " parr-markings " 

 disappear in the migratory series upon their first descent to the 

 sea, and are seen no more. So also do they disappear in 

 such brook or lake trout as abundance of food enables to 

 develop to a large size. But where food is scarce or water 

 scanty, or where trout multiply unchecked beyond the natural 

 resources of a lake, the fish never attain what may be reckoned 

 the average size of their species ; they are stunted in growth, 

 and retain the finger-marks throughout life. This tends to the 

 conclusion that these markings were part of the normal livery 

 of primitive trout ; the inference being that, at no very distant 

 date, all salmon, trout, and char were comprised in a single 

 species ; that the more vigorous members of the race acquired 

 by degrees the habit of resorting to the sea for food which the 

 fresh water could not supply in sufficient quantity ; and that 

 their changed habits and exposure to the vicissitudes of 

 migration produced such permanent organic changes as 

 differentiate the species. In many respects the subject remains 

 very obscure ; for example, it is not apparent why, if the 

 explanation offered above is the true one, there should be 

 different species of migratory salmonoid fish frequenting the 

 same river. If these are all descended from common ancestors 

 trout why are they not all true salmon, or salmon-trout, or 



