6 THE LIFE OF THE SALMON 
form part inhabit permanently the sea, the clupeids, 
or herring tribe, which are their nearest allies, being 
certainly of marine origin, as proved by their abun- 
dance in cretaceous seas, yet a few, like the shads, 
ascending rivers to spawn without this ever having 
been adduced as evidence in favour of a fresh water 
origin of the family to which they belong.” 
The more we learn about the salmon, the more we 
have to realise the very considerable amount of time 
which it apparently spends in the sea. Sea trout 
are chiefly estuarial in habit. Loch Leven trout 
may very possibly be sea trout, or at any rate 
migratory trout—which amounts to much the same 
thing—shut off from the sea. It is easy by a little 
judicious feeding to make them practically indis- 
tinguishable from ordinary sea trout. Brown trout 
taken from Dorsetshire to New Zealand quickly 
acquired a migratory habit and became large silvery 
fish, inhabiting the sea for the most part, and ascend- 
ing rivers to spawn. The brown trout which I have 
referred to at the mouth of the Tay were clearly 
doing the same, while in localities such as Orkney 
and Shetland and the Outer Hebrides we have the 
established tidal variety which has been called S. 
orcadensis; and in the West of Ireland we have 
S. estuarwus, the so-called slob trout. I do not agree 
that there is any specific distinction, any more than 
T agree that a ferox is not a brown trout. In all 
these examples we may say that to feed is in one 
sense the impulse which causes the change of habit 
and consequent modification ; and in the same way, 
taking salmonids as we now find them, it is evident 
