his "The Colours of Animals," International
Scientific Series, 1890: and in F. E. Beddard's "Animal
Colouration"; London, Swan Sonnenschein; N. Y., Macmillan,
1892.]

There is no more convincing proof of the truth of a comprehensive
theory, than its power of absorbing and finding a place for new facts,
and its capability of interpreting phenomena which had been previously
looked upon as unaccountable anomalies. It is thus that the law of
universal gravitation and the undulatory theory of light have become
established and universally accepted by men of science. Fact after fact
has been brought forward as being apparently inconsistent with them, and
one after another these very facts have been shown to be the
consequences of the laws they were at first supposed to disprove. A
false theory will never stand this test. Advancing knowledge brings to
light whole groups of facts which it cannot deal with, and its advocates
steadily decrease in numbers, notwithstanding the ability and
scientific skill with which it has been supported. The course of a true
theory 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.

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 races which possess them. This great principle gives
us a clue which we can follow out in the study of many recondite
phenomena, and leads us to seek a meaning and a purpose of some definite
character in minu