short duration. Even now that we have acquired some
idea of the lapse of time, men are too apt to assume without proof that
the geological record is so perfect that it would have afforded plain
evidence of the mutation of species if they had really undergone
mutation. The chief cause, however, of the once-prevalent unwillingness
to admit that one species has given birth to other and distinct species
is the fact that men are slow to admit great changes of which they do
not see the steps. The difficulty is the same which was experienced by
many geologists when Lyell first insisted that long lines of inland
cliffs had been formed and great valleys excavated, not by catastrophes,
but by the slow-moving agencies which we see still at work. The human
mind cannot grasp the full meaning of the term of even a million years;
cannot add up and perceive the full effects of many slight variations
accumulated during an almost infinite number of generations.

When the first edition of the "Origin of Species" was published in 1859,
Darwin wrote that he by no means expected to convince experienced
naturalists whose minds were stocked with a multitude of facts, all
regarded during a long course of years from a point of view directly
opposite to his. He looked forward with confidence, however, to the
future, to young and rising naturalists, who would be able to view both
sides of the question with impartiality. He predicted that, when the
conclusions reached by him and by Mr. Wallace concerning the origin of
species should be generally accepted, there would be a considerable
revolution in natural history. Naturalists, for instance, would be
forced to acknowledge that the only distinction between species and
well-marked varieties is that the latter are known or believed to be
connected at the present day by intermediate gradations, whereas species
were formerly, though they are not now, thus connected. It might thus
come to pass that forms generally acknowledged in 1859 to be merely
varieties, would thereafter be thought worthy of specific names; in
which case scientific and common language would come into accordance. In
short, Darwin looked forward to the time when species would have to be
treated in the same manner as genera are treated by those naturalists
who admit that genera are merely artificial combinations made for
convenience.

Darwin also foresaw that when his theory of the origin of species should
be adopted, other and more g