bly protected by their
assimilative hues. The stonechats, the larks, the quails, the
goatsuckers and the grouse, which abound in the North African and
Asiatic deserts, are all tinted and mottled so as to resemble with
wonderful accuracy the average colour and aspect of the soil in the
district they inhabit. The Rev. H. Tristram, in his account of the
ornithology of North Africa in the 1st volume of the "Ibis," says: "In
the desert, where neither trees, brush-wood, nor even undulation of the
surface afford the slightest protection to its foes, a modification of
colour which shall be assimilated to that of the surrounding country, is
absolutely necessary. Hence _without exception_ the upper plumage of
_every bird_, whether lark, chat, sylvain, or sand-grouse, and also the
fur of _all the smaller mammals_, and the skin of _all the snakes and
lizards_, is of one uniform isabelline or sand colour." After the
testimony of so able an observer it is unnecessary to adduce further
examples of the protective colours of desert animals.

Almost equally striking are the cases of arctic animals possessing the
white colour that best conceals them upon snowfields and icebergs. The
polar bear is the only bear that is white, and it lives constantly among
snow and ice. The arctic fox, the ermine and the alpine hare change to
white in winter only, because in summer white would be more conspicuous
than any other colour, and therefore a danger rather than a protection;
but the American polar hare, inhabiting regions of almost perpetual
snow, is white all the year round. Other animals inhabiting the same
Northern regions do not, however, change colour. The sable is a good
example, for throughout the severity of a Siberian winter it retains its
rich brown fur. But its habits are such that it does not need the
protection of colour, for it is said to be able to subsist on fruits and
berries in winter, and to be so active upon the trees as to catch small
birds among the branches. So also the woodchuck of Canada has a
dark-brown fur; but then it lives in burrows and frequents river banks,
catching fish and small animals that live in or near the water.

Among birds, the ptarmigan is a fine example of protective colouring.
Its summer plumage so exactly harmonizes with the lichen-coloured stones
among which it delights to sit, that a person may walk through a flock
of them without seeing a single bird; while in winter its white plumage
is an almost e