the globe. The white of arctic animals, the
yellowish tints of the desert forms, the dusky hues of crepuscular and
nocturnal species, the transparent or bluish tints of oceanic creatures,
represent a vast host in themselves; but we have an equally numerous
body whose tints are adapted to tropical foliage, to the bark of trees,
or to the soil or dead leaves on or among which they habitually live.
Then we have the innumerable special adaptations to the tints and forms
of leaves, or twigs, or flowers; to bark or moss; to rock or pebble; by
which such vast numbers of the insect tribes obtain protection; and we
have seen that these various forms of coloration are equally prevalent
in the waters of the seas and oceans, and are thus coextensive with the
domain of life upon the earth. The comparatively small numbers which
possess "terrifying" or "alluring" coloration may be classed under the
general head of the protectively coloured.

But under the next head--colour for recognition--we have a totally
distinct category, to some extent antagonistic or complementary to the
last, since its essential principle is visibility rather than
concealment. Yet it has been shown, I think, that this mode of
coloration is almost equally important, since it not only aids in the
preservation of existing species and in the perpetuation of pure races,
but was, perhaps, in its earlier stages, a not unimportant factor in
their development. To it we owe most of the variety and much of the
beauty in the colours of animals; it has caused at once bilateral
symmetry and general permanence of type; and its range of action has
been perhaps equally extensive with that of coloration for concealment.

_Influence of Locality or of Climate on Colour._

Certain relations between locality and coloration have long been
noticed. Mr. Gould observed that birds from inland or continental
localities were more brightly coloured than those living near the
sea-coast or on islands, and he supposed that the more brilliant
atmosphere of the inland stations was the explanation of the
phenomenon.[90] Many American naturalists have observed similar facts,
and they assert that the intensity of the colours of birds and mammals
increases from north to south, and also with the increase of humidity.
This change is imputed by Mr. J.A. Allen to the direct action of the
environment. He says: "In respect to the correlation of intensity of
colour in animals with the degree of humidit