to the
fact that singing birds are all small, and suggesting (but I think
erroneously) that this may have arisen from the difficulty larger birds
would have in concealing themselves if they called the attention of
their enemies by loud notes, goes on thus:--"I should rather conceive it
is for the same reason no hen bird sings, because this talent would be
still more dangerous during incubation, which _may possibly also account
for the inferiority in point of plumage_." This is a curious
anticipation of the main idea on which this essay is founded. It has
been unnoticed for near a century, and my attention was only recently
called to it by Mr. Darwin himself.

_Conclusion._

To some persons it will perhaps appear, that the causes to which I
impute so much of the external aspect of nature are too simple, too
insignificant, and too unimportant for such a mighty work. But I would
ask them to consider, that the great object of all the peculiarities of
animal structure is to preserve the life of the individual, and to
maintain the existence of the species. Colour has hitherto been too
often looked upon as something adventitious and superficial, something
given to an animal not to be useful to itself, but solely to gratify man
or even superior beings--to add to the beauty and ideal harmony of
nature. If this were the case, then, it is evident that the colours of
organised beings would be an exception to most other natural phenomena.
They would not be the product of general laws, or determined by
ever-changing external conditions; and we must give up all enquiry into
their origin and causes, since (by the hypothesis) they are dependent on
a Will whose motives must ever be unknown to us. But, strange to say, no
sooner do we begin to examine and classify the colours of natural
objects, than we find that they are intimately related to a variety of
other phenomena, and are, like them, strictly subordinated to general
laws. I have here attempted to elucidate some of these laws in the case
of birds, and have shown how the mode of nidification has affected the
colouring of the female sex in this group. I have before shown to how
great an extent, and in how many ways, the need of protection has
determined the colours of insects, and of some groups of reptiles and
mammalia, and I would now call particular attention to the fact that the
gay tints of flowers, so long supposed to be a convincing proof that
colour has been bestowed for