ved
forwards for the next stroke.]

[Illustration: THE BIG ROBBER-CRAB (_Birgus Latro_), THAT CLIMBS THE
COCO-NUT PALM AND BREAKS OFF THE NUTS

It occurs on islands in the Indian Ocean and Pacific, and is often found
far above sea-level. It is able to breathe dry air. One is seen emerging
from its burrow, which is often lined with coco-nut fibre. The empty
coco-nut shell is sometimes used by the Robber-Crab for the protection
of its tail.]

Now what happened in this kingdom of Caledonia which Neolithic Man had
found? He began to introduce domesticated animals, and that meant a
thinning of the ranks of predacious creatures. "Safety first" was the
dangerous motto in obedience to which man exterminated the lynx, the
brown bear, and the wolf. Other creatures, such as the great auk, were
destroyed for food, and others like the marten for their furs. Small
pests were destroyed to protect the beginnings of agriculture; larger
animals like the boar were hunted out of existence; others, like the
pearl-bearing river-mussels, yielded to subtler demands. No doubt there
was protection also--protection for sport, for utility, for aesthetic
reasons, and because of humane sentiments; even wholesome superstitions
have safeguarded the robin redbreast and the wren. There were
introductions too--the rabbit for utility, the pheasant for sport, and
the peacock for amenity. And every introduction, every protection, every
killing out had its far-reaching influences.

But if we are to picture the evolution going on, we must think also of
man's indirect interference with animal life. He destroyed the forests,
he cultivated the wild, he made bridges, he allowed aliens, like rats
and cockroaches, to get in unawares. Of course, he often did good, as
when he drained swamps and got rid of the mosquitoes which once made
malaria rife in Scotland.

What has been the net result? Not, as one might think for a moment, a
reduction in the _number_ of different kinds of animals. Fourteen or so
species of birds and beasts have been banished from Scotland since man
interfered, but as far as numbers go they have been more than replaced
by deliberate introductions like fallow deer, rabbit, squirrel, and
pheasant, and by accidental introductions like rats and cockroaches. But
the change is rather in _quality_ than in quantity; the smaller have
taken the place of the larger, rather paltry pigmies of noble giants.
Thus we get a vivid idea that evolution, espec