invisibility may save it from the
hungry eyes of golden eagles.

Similarly the brown stoat becomes the white ermine, mainly by the
growth, of a new suit of white fur, and the same is true of the mountain
hare. The ermine is all white except the black tip of its tail; the
mountain hare in its winter dress is all white save the black tips of
its ears. In some cases, especially in the mountain hare, it seems that
individual hairs may turn white, by a loss of pigment, as may occur in
man. According to Metchnikoff, the wandering amoeboid cells of the
body, called phagocytes, may creep up into the hairs and come back again
with microscopic burdens of pigment. The place of the pigment is taken
by gas-bubbles, and that is what causes the whiteness. In no animals is
there any white _pigment_; the white _colour_ is like that of snow or
foam, it is due to the complete reflection of the light from innumerable
minute surfaces of crystals or bubbles.

[Illustration: _Photo: W. S. Berridge, F.Z.S._

BANDED KRAIT: A VERY POISONOUS SNAKE WITH ALTERNATING YELLOW AND DARK
BANDS

It is very conspicuous and may serve as an illustration of warning
coloration. Perhaps, that is to say, its striking coloration serves as
an advertisement, impressing other creatures with the fact that the
Banded Krait should be left alone. It is very unprofitable for a snake
to waste its venom on creatures it does not want.]

[Illustration: _Photos: W. S. Berridge, F.Z.S._

THE WARTY CHAMELEON

The upper photograph shows the Warty Chameleon inflated and conspicuous.
At another time, however, with compressed body and adjusted coloration,
the animal is very inconspicuous. The lower photograph shows the sudden
protrusion of the very long tongue on a fly.]

[Illustration: SEASONAL COLOUR-CHANGE: A SUMMER SCENE IN NORTH
SCANDINAVIA

Showing a brown Variable Hare, Willow Grouse, and Arctic Fox, all
inconspicuous in their coloration when seen in their natural
surroundings.]

The mountain hare may escape the fox the more readily because its
whiteness makes it so inconspicuous against a background of snow; and
yet, at other times, we have seen the creature standing out like a
target on the dark moorland. So it cuts both ways. The ermine has almost
no enemies except the gamekeeper, but its winter whiteness may help it
to sneak upon its victims, such as grouse or rabbit, when there is snow
upon the ground. In both cases, however, the probability is that the
co