changes, or from the immigrations and emigrations of other
species living on contiguous geographical areas), it follows that the
process of natural selection need never reach a terminal phase. And
forasmuch as natural selection may thus continue, _ad infinitum_, slowly
to alter a specific type in adaptation to a gradually changing
environment, if in any case the alteration thus effected is sufficient
in amount to lead naturalists to denote the specific type by some
different name, it follows that natural selection has transmuted one
specific type into another. And so the process is supposed to go on over
all the countless species of plants and animals simultaneously--the
world of organic types being thus regarded as in a state of perpetual,
though gradual, flux.

Such, then, is the theory of natural selection, or survival of the
fittest; and the first thing we have to notice with regard to it is,
that it offers to our acceptance a scientific explanation of the
numberless cases of apparent design which we everywhere meet with in
organic nature. For all such cases of apparent design consist only in
the _adaptation_ which is shown by organisms to their environment, and
it is obvious that the facts are covered by the theory of natural
selection no less completely than they are covered by the theory of
intelligent design. Perhaps it may be answered,--"The fact that these
innumerable cases of adaptation may be accounted for by natural
selection is no proof that they are not really due to intelligent
design." And, in truth, this is an objection which is often urged by
minds--even highly cultured minds--which have not been accustomed to
scientific modes of thought. I have heard an eminent professor tell his
class that the many instances of adaptation which Mr. Darwin discovered
and described as occurring in orchids, seemed to him to tell more in
favour of contrivance than in favour of natural causes; and another
eminent professor once wrote to me that although he had read the
_Origin of Species_ with care, he could see in it no evidence of natural
selection which might not equally well be adduced in favour of
intelligent design. But here we meet with a radical misconception of the
whole logical attitude of science. For, be it observed, the exception
_in limine_ to the evidence which we are about to consider, does not
question that natural selection _may_ not be able to do all that Mr.
Darwin ascribes to it: it merely objects t