52 Animal Life 
seldom appear. Here is an example. Three rivers—the Cree, the Palnure, and the 
Bladenoch—fall into a common estuary at the head of Wigtown Bay, in the Solway. All 
three are frequented by salmon, but I have never seen a salmon-trout above the tidal 
water in the Bladenoch. The whole body of them passes into the other two rivers, whereof 
one, the Palnure, is not more than a fifth m volume of the Bladenoch—a mere mountain 
burn, in fact. The Cree, by far the largest of the three rivers, draws great numbers of 
salmon-trout; but before they have run far up they turn aside into a fourth stream, the 
Penkiln, of dimensions as insignificant as the Palnure. They thus desert the ample 
channel of the Cree, with thirty miles of spawning ground, for the narrow and inconvenient 
quarters of the PenkilIn. In other salmon rivers of the district it is different; salmon- 
trout push right away up into the headwaters and spawn mm company with the salmon. 
like all migratory 
salmonoid fish, the different 
species and varieties of sea- 
trout probably have descended 
from common and not very 
remote ancestors. Strong 
evidence of the close relation- 
ship, uf not the common 
ancestry, of all British 
salmonoid fish, is furnished 
by their similarity in youth. 
The yearlings of all species, 
' so far as has been ascer- 
tained—salmon, migratory 
' trout, brook and lake trout, 
and grayhng—are barred; as 
well as spotted. In coloura- 
tion they are hardly to be distinguished from each other, though migratory trout usually 
show two more bars than brook-trout. When the young salmon-trout is about to start 
seawards, all the bars and most of the spots disappear under a beautiful silvery coat. 
Brook-trout, also, when allowed sufficient food and space to develop freely, lose their bars 
and often change their spots, becoming, under certain conditions, almost as silvery as 
sea-going fish. But when fare is scanty and quarters narrow, they retain their juvenile 
colouring and marking through life, thereby suggesting that these are the primitive livery 
of the family. Yet, supposing that European salmon and migratory trout have sprung 
from the same ancestry as our common river trout, it is perplexing to’ account for their 
specific differences. Inhabiting the same waters, alternately fresh and salt, migrating to 
and fro at the same seasons, it might have been expected that they would develop 
identical characteristics. 
Fresh light may be thrown soon upon the problem by what is going on in the waters 
of New Zealand. Common English brook-trout, introduced there, have thriven wonderfully 
and attain a great size in a relatively short time. Attempts to acclimatise salmon and 
salmon-trout in the southern hemisphere have met with uniform failure; but it is most 
interesting to note that no sooner had the brook-trout made themselves perfectly at home 
there than they acquired the sea-going habit and have been taken in the salt water of 
great size-and with .coats as -silvery—as~-salmon~ or~salmon-trout.:~ Practically, they have 
become a fine race of salmon-trout. Here we seem to witness, re-enacted under our eyes, 
the process by which the different species of , 
migratory trout were originally established. 
i 
Photograph by R- Thiele & Co., Chancery Lane 
SALMON-TROUT (Salmo trutta). 
