must, sooner or later, "improve" its progenitor from the face of the
earth, and take its place. If circumstances change, the victor will be
similarly supplanted by its own progeny; and thus, by the operation of
natural causes, unlimited modification may in the lapse of long ages
occur.

For an explanation of what I have here called vaguely "surrounding
circumstances," and of why they continually change--for ample proof
that the "struggle for existence" is a very great reality, and
assuredly 'tends' to exert the influence ascribed to it--I must refer to
Mr. Darwin's book. I believe I have stated fairly the position upon
which his whole theory must stand or fall; and it is not my purpose to
anticipate a full review of his work. If it can be proved that the
process of natural selection, operating upon any species, can give rise
to varieties of species so different from one another that none of our
tests will distinguish them from true species, Mr. Darwin's hypothesis
of the origin of species will take its place among the established
theories of science, be its consequences whatever they may. If, on the
other hand, Mr. Darwin has erred, either in fact or in reasoning, his
fellow-workers will soon find out the weak points in his doctrines, and
their extinction by some nearer approximation to the truth will
exemplify his own principle of natural selection.

In either case the question is one to be settled only by the
painstaking, truth-loving investigation of skilled naturalists. It is
the duty of the general public to await the result in patience; and,
above all things, to discourage, as they would any other crimes, the
attempt to enlist the prejudices of the ignorant, or the
uncharitableness of the bigoted, on either side of the controversy.