apacity for continued existence and increase. We know, further, that
varieties of many other tints occasionally occur; and as "the survival
of the fittest" must inevitably weed out those whose colours are
prejudicial and preserve those whose colours are a safeguard, we require
no other mode of accounting for the protective tints of arctic and
desert animals. But this being granted, there is such a perfectly
continuous and graduated series of examples of every kind of protective
imitation, up to the most wonderful cases of what is termed "mimicry,"
that we can find no place at which to draw the line and say,--so far
variation and natural selection will account for the phenomena, but for
all the rest we require a more potent cause. The counter theories that
have been proposed, that of the "special creation" of each imitative
form, that of the action of similar "conditions of existence" for some
of the cases, and of the laws of "hereditary descent and the reversion
to ancestral forms" for others,--have all been shown to be beset with
difficulties, and the two latter to be directly contradicted by some of
the most constant and most remarkable of the facts to be accounted for.

The important part that protective "resemblance" has played in
determining the colours and markings of many groups of animals will
enable us to understand the meaning of one of the most striking facts in
nature, the uniformity in the colours of the vegetable as compared with
the wonderful diversity of the animal world. There appears no good
reason why trees and shrubs should not have been adorned with as many
varied hues and as strikingly designed patterns as birds and
butterflies, since the gay colours of flowers show that there is no
incapacity in vegetable tissues to exhibit them. But even flowers
themselves present us with none of those wonderful designs, those
complicated arrangements of stripes and dots and patches of colour, that
harmonious blending of hues in lines and bands and shaded spots, which
are so general a feature in insects. It is the opinion of Mr. Darwin
that we owe much of the beauty of flowers to the necessity of attracting
insects to aid in their fertilization, and that much of the development
of colour in the animal world is due to "sexual selection," colour being
universally attractive, and thus leading to its propagation and
increase; but while fully admitting this, it will be evident from the
facts and arguments here brought