investigated. If any naturalist had been asked at that day whether,
supposing it to be clearly shown that all the different species of each
genus had been derived from some one ancestral species, and that a full
and complete explanation were to be given of how each minute difference
in form, colour, or structure might have originated, and how the
several peculiarities of habit and of geographical distribution might
have been brought about--whether, if this were done, the "origin of
species" would be discovered, the great mystery solved, he would
undoubtedly have replied in the affirmative. He would probably have
added that he never expected any such marvellous discovery to be made in
his lifetime. But so much as this assuredly Mr. Darwin has done, not
only in the opinion of his disciples and admirers, but by the admissions
of those who doubt the completeness of his explanations. For almost all
their objections and difficulties apply to those larger differences
which separate genera, families, and orders from each other, not to
those which separate one species from the species to which it is most
nearly allied, and from the remaining species of the same genus. They
adduce such difficulties as the first development of the eye, or of the
milk-producing glands of the mammalia; the wonderful instincts of bees
and of ants; the complex arrangements for the fertilisation of orchids,
and numerous other points of structure or habit, as not being
satisfactorily explained. But it is evident that these peculiarities had
their origin at a very remote period of the earth's history, and no
theory, however complete, can do more than afford a probable conjecture
as to how they were produced. Our ignorance of the state of the earth's
surface and of the conditions of life at those remote periods is very
great; thousands of animals and plants must have existed of which we
have no record; while we are usually without any information as to the
habits and general life-history even of those of which we possess some
fragmentary remains; so that the truest and most complete theory would