e desert regions of the earth we find an even more general
accordance of colour with surroundings. The lion, the camel, and all the
desert antelopes have more or less the colour of the sand or rock among
which they live. The Egyptian cat and the Pampas cat are sandy or earth
coloured. The Australian kangaroos are of similar tints, and the
original colour of the wild horse is supposed to have been sandy or clay
coloured. Birds are equally well protected by assimilative hues; the
larks, quails, goatsuckers, and grouse which abound in the North African
and Asiatic deserts are all tinted or mottled so as closely to resemble
the average colour of the soil in the districts they inhabit. Canon
Tristram, who knows these regions and their natural history so well,
says, in an often quoted passage: "In the desert, where neither trees,
brushwood, nor even undulations 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."

Passing on to the tropical regions, it is among their evergreen forests
alone that we find whole groups of birds whose ground colour is green.
Parrots are very generally green, and in the East we have an extensive
group of green fruit-eating pigeons; while the barbets, bee-eaters,
turacos, leaf-thrushes (Phyllornis), white-eyes (Zosterops), and many
other groups, have so much green in their plumage as to tend greatly to
their concealment among the dense foliage. There can be no doubt that
these colours have been acquired as a protection, when we see that in
all the temperate regions, where the leaves are deciduous, the ground
colour of the great majority of birds, especially on the upper surface,
is a rusty brown of various shades, well corresponding with the bark,
withered leaves, ferns, and bare thickets among which they live in
autumn and winter, and especially in early spring when so many of them
build their nests.

Nocturnal animals supply another illustration of the same rule, in the
dusky colours of mice, rats, bats, and moles, and in the soft mottled
plumage of owls and goatsuckers which, while almost equally
inconspicuous in the twilight, are such as to f