ng. It is safe to say that in process of time wide departures from
the safest coloration will be wiped out in the course of Nature's
ceaseless sifting.

But we must not be credulous, and there are three cautions to be borne
in mind. (1) An animal may be very like its surroundings without there
being any protection implied. The arrow-worms in the sea are as clear as
glass, and so are many open-sea animals. But this is because their
tissues are so watery, with a specific gravity near that of the salt
water. And the invisibility does not save them, always or often, from
being swallowed by larger animals that gather the harvest of the sea.
(2) Among the cleverer animals it looks as if the creature sometimes
sought out a spot where it was most inconspicuous. A spider may place
itself in the middle of a little patch of lichen, where its
self-effacement is complete. Perhaps it is more comfortable as well as
safer to rest in surroundings the general colour of which is like that
of the animal's body. (3) The fishes that live among the coral-reefs are
startling in their brilliant coloration, and there are many different
patterns. To explain this it has been suggested that these fishes are so
safe among the mazy passages and endless nooks of the reefs, that they
can well afford to wear any colour that suits their constitution. In
some cases this may be true, but naturalists who have put on a diving
suit and walked about among the coral have told us that each kind of
fish is particularly suited to some particular place, and that some are
suited for midday work and others for evening work. Sometimes there is a
sort of Box and Cox arrangement by which two different fishes utilise
the same corner at different times.

[Illustration: THE PRAYING MANTIS (_Mantis Religiosa_)

A very voracious insect with a quiet, unobtrusive appearance. It holds
its formidable forelegs as if in the attitude of prayer; its movements
are very slow and stealthy; and there is a suggestion of a leaf in the
forewing. But there is no reason to credit the creature with conscious
guile!]

[Illustration: PROTECTIVE COLORATION: A WINTER SCENE IN NORTH
SCANDINAVIA

Showing Variable Hare, Willow Grouse, and Arctic Fox, all white in
winter and inconspicuous against the snow. But the white dress is also
the dress that is physiologically best, for it loses least of the animal
heat.]

[Illustration: THE VARIABLE MONITOR (_Varanus_)

The monitors are the largest o