two years these are double that length. Usually in the second year,
but it may be earlier or later, the parr become silvery _smolts_, which
go out to sea, usually about the month of May. They feed on young
herring and the like and grow large and strong. When they are about
three and a half years old they come up the rivers as _grilse_ and may
spawn. Or they may pass through the whole grilse stage in the sea and
come up the rivers with all the characters of the full-grown fish. In
many cases the salmon spawn only once, and some (they are called _kelts_
after spawning) are so much exhausted by starting a new generation that
they die or fall a victim to otters and other enemies. In the case of
the salmon of the North Pacific (in the genus _Oncorhynchus_, not
_Salmo_) all the individuals die after spawning, none being able to
return to the sea. It must be remembered that full-grown salmon do not
as a rule feed in fresh water, though they may be unable to resist
snapping at the angler's strange creations. A very interesting fact is
that the salmon keeps as it were a diary of its movements, which vary a
good deal in different rivers. This diary is written in the scales, and
a careful reading of the concentric lines on the scales shows the age of
the fish, and when it went out to sea, and whether it has spawned or
not, and more besides.

Interpretation of the Salmon's Story

When an animal frequents two different haunts, in one of which it
breeds, it is very often safe to say that the breeding-place represents
the original home. The flounder is quite comfortable far up the rivers,
but it has to go to the shore-waters to spawn, and there is no doubt
that the flounder is a marine fish which has recently learned to
colonise the fresh waters. Its relatives, like plaice and sole, are
strictly marine. But it is impossible to make a dogma of the rule that
the breeding-place corresponds to the original home. Thus some kinds of
bass, which belong to the marine family of sea-perches, live in the sea
or in estuaries, while two have become permanent residents in fresh
water. Or, again, the members of the herring family are very
distinctively marine, but the shad, which belong to this family, spawn
in rivers and may spend their lives there.

So there are two different ways of interpreting the life-history of the
salmon. Some authorities regard the salmon as a marine fish which is
establishing itself in fresh water. But others read the