obber-crab with
the coco-palm, for that tree is not a native of these coral islands, but
has been introduced, perhaps from Mexico, by the Polynesian mariners
before the discovery of America by Columbus. So the learning to deal
with coconuts is a recent achievement, and we are face to face with a
very good example of evolution going on.

[Illustration: EARLY LIFE-HISTORY OF THE SALMON

1. The fertilised egg, shed in the gravelly bed of the river.

2. The embryo within the egg, just before hatching. The embryo has been
constricted off from the yolk-laden portion of the egg.

3. The newly hatched salmon, or alevin, encumbered with its legacy of
yolk (Y.S.).

4 and 5. The larval salmon, still being nourished from the yolk-sac
(Y.S.), which is diminishing in size as the fish grows larger.

6. The salmon fry about six weeks old, with the yolk fully absorbed, so
that the young fish has now to feed for itself. The fry become parr,
which go to the sea as smolts, and return as grilse.

In all cases the small figures to the right indicate the natural size.]

[Illustration: THE SALMON LEAPING AT THE FALL IS A MOST FASCINATING
SPECTACLE

Again and again we see them jumping out of the seething foam beneath the
fall, casting themselves into the curtain of the down-rushing water,
only to be carried back by it into the depths whence they have risen.
One here and another there makes its effort good, touches the upper lip
of the cataract, gives a swift stroke of its tail, and rushes on towards
those upper reaches which are the immemorial spawning beds of its
race.]

The Story of the Salmon

In late autumn or in winter the salmon spawn in the rivers. The female
makes a shallow trough in the gravel by moving her tail from side to
side, and therein lays many eggs. The male, who is in attendance,
fertilises these with the milt, and then the female covers them deeply
with gravel. The process is repeated over and over again for a week or
more till all the eggs are shed. For three to four months the eggs
develop, and eventually there emerge the larvae or _alevins_, which lurk
among the pebbles. They cannot swim much, for they are encumbered by a
big legacy of yolk. In a few weeks, perhaps eight, the protruding bag of
yolk has disappeared and the _fry_, about an inch long, begin to move
about more actively and to fend for themselves. By the end of the year
they have grown to be rather trout-like _parr_, about four inches long.
In