established if it had had any germ of truth in it; yet it quite
died out in a few short years, its very existence is now a matter of
history; and so rapid was its fall that its talented creator, Swainson,
perhaps lived to be the last man who believed in it.

Such is the course of a false theory. That of a true one is very
different, as may be well seen by the progress of opinion on the subject
of Natural Selection. In less than eight years "The Origin of Species"
has produced conviction in the minds of a majority of the most eminent
living men of science. New facts, new problems, new difficulties as they
arise are accepted, solved or removed by this theory; and its principles
are illustrated by the progress and conclusions of every well
established branch of human knowledge. It is the object of the present
essay to show how it has recently been applied to connect together and
explain a variety of curious facts which had long been considered as
inexplicable anomalies.

_Importance of the Principle of Utility._

Perhaps no principle has ever been announced so fertile in results as
that which Mr. Darwin so earnestly impresses upon us, and which is
indeed a necessary deduction from the theory of Natural Selection,
namely--that none of the definite facts of organic nature, no special
organ, no characteristic form or marking, no peculiarities of instinct
or of habit, no relations between species or between groups of
species--can exist, but which must now be or once have been _useful_ to
the individuals or the races which possess them. This great principle
gives us a clue which we can follow out in the study of many recondite
phaenomena, and leads us to seek a meaning and a purpose of some definite
character in minutiae which we should be otherwise almost sure to pass
over as insignificant or unimportant.

_Popular Theories of Colour in Animals._

The adaptation of the external colouring of animals to their conditions
of life has long been recognised, and has been imputed either to an
originally created specific peculiarity, or to the direct action of
climate, soil, or food. Where the former explanation has been accepted,
it has completely checked inquiry, since we could never get any further
than the fact of the adaptation. There was nothing more to be known
about the matter. The second explanation was soon found to be quite
inadequate to deal with all the varied phases of the phaenomena, and to
be contradicted by ma