ed _on
the theory of descent with modification_ are serious enough;"[359] and
in the next paragraph, "As, according to _the theory of natural
selection, &c._," the context showing that in each case descent with
modification is intended.

Again:--

"On the theory of the _natural selection_ of successive, slight, but
profitable, modifications,"[360] that is to say, on the theory of the
survival of the fittest; while on the next page we find "_the theory of
descent with modification_," and "_the principle of natural selection_,"
used as though they were convertible terms.

Again:--

"The existence of closely allied or representative species in any two
areas implies, _on the theory of descent with modification, &c._;"[361]
and, in the next paragraph, "_the theory of natural selection_, with its
contingencies of extinction and divergence of character," is substituted
as though the two expressions were identical.

This is calculated to mislead. Independently of the fact that "natural
selection," or "the survival of the fittest," is in no sense a theory,
but simply an observed fact, yet even if the words are allowed to stand
for "descent with modification by means of natural selection," it is
still misleading to write as though this were synonymous with "the
theory of evolution," or "the theory of descent with modification." To
do this prevents the reader from bearing in mind that "evolution by
means of the circumstance-suiting power of plants and animals" as
advanced by the earlier evolutionists; and "evolution by means of lucky
accidents" with comparatively little circumstance-suiting power, are two
very different things, of which the one may be true and the other
untrue. It leads the reader to forget that evolution by no means stands
or falls with evolution by means of natural selection, and makes him
think that if he accepts evolution at all, he is bound to Mr. Darwin's
view of it. Hence, when he falls in with such writers as Professor
Mivart and the Rev. J. J. Murphy, who show, and very plainly, that the
survival of the fittest, unsupplemented by something which shall give a
definite aim to the variations which successively occur, fails to
account for the coadaptations of need and structure, he imagines that
evolution has much less to say for itself than it really has. If Mr.
Darwin, instead of taking the line which he has thought fit to adopt
towards Buffon, Dr. Erasmus Darwin, Lamarck, and the author of the
'Vest