forth two distinct and contradictory theories of the
functions of natural selection. According to the one theory natural
selection is selective or preservative, and nothing more. According
to the other theory natural selection creates the variations(!) ...
It certainly seems absurd to speak of natural selection, or the
struggle for existence, as selective or preservative, for the
struggle for existence does not preserve at all, not even the fit
variations, as both the fit and the unfit struggle for existence,
the unfit naturally more than the fit, and the fit are preserved,
not in consequence of the struggle, but in consequence of their
fitness. Suppose two varieties of the same species are driven, by an
increase of their numbers, to seek for subsistence in a colder
region than they have been accustomed to, and that one of these
varieties had a hardier constitution than the other; and let us
suppose that the former withstood the severe climate better than the
latter, and consequently survived, while the other perished. In this
case the hardier survived, not because of the struggle, but because
it had a constitution better adapted to the climate. I wish to
ascertain if a certain metal in my possession is gold or some baser
metal, and I apply the usual test; but the mere fact of my testing
this metal would not make it gold or any other kind of metal."

I have thought it worth while to quote this passage for the sake of
showing the extraordinary confusion of mind which still prevails on
the part of Darwin's critics, even with reference to the very
fundamental parts of his theory. For, as I have said, the writer of
this passage shows himself a shrewd critic in some other parts of
his essay, where he is not engaged especially on the theory of
natural selection.

I will now pass on to consider another misconception of the Darwinian
theory, which is very prevalent in the public mind. It is virtually
asked, If some species are supposed to have been improved by natural
selection, why have not all species been similarly improved? Why should
not all invertebrated animals have risen into vertebrated? Or why
should not all monkeys have become men?

The answers are manifold. In the first place, it by no means follows
that because an advance in organization has proved itself of benefit in
the case of one form of life, therefor