hole, then, I submit, not only has it not been proved that an
"enormous number of specific peculiarities" are useless, and that, as a
logical result, natural selection is "not a theory of the origin of
species," but only of the origin of adaptations which are usually
common to many species, or, more commonly, to genera and families; but,
I urge further, it has not even been proved that any truly "specific"
characters--those which either singly or in combination distinguish each
species from its nearest allies--are entirely unadaptive, useless, and
meaningless; while a great body of facts on the one hand, and some
weighty arguments on the other, alike prove that specific characters
have been, and could only have been, developed and fixed by natural
selection because of their utility. We may admit, that among the great
number of variations and sports which continually arise many are
altogether useless without being hurtful; but no cause or influence has
been adduced adequate to render such characters fixed and constant
throughout the vast number of individuals which constitute any of the
more dominant species.[47]

_The Swamping Effects of Intercrossing._

This supposed insuperable difficulty was first advanced in an article in
the _North British Review_ in 1867, and much attention has been
attracted to it by the acknowledgment of Mr. Darwin that it proved to
him that "single variations," or what are usually termed "sports," could
very rarely, if ever, be perpetuated in a state of nature, as he had at
first thought might occasionally be the case. But he had always
considered that the chief part, and latterly the whole, of the materials
with which natural selection works, was afforded by individual
variations, or that amount of ever fluctuating variability which exists
in all organisms and in all their parts. Other writers have urged the
same objection, even as against individual variability, apparently in
total ignorance of its amount and range; and quite recently Professor
G.J. Romanes has adduced it as one of the difficulties which can alone
be overcome by his theory of physiological selection. He urges, that the
same variation does not occur simultaneously in a number of individuals
inhabiting the same area, and that it is mere assumption to say it does;
while he admits that "if the assumption were granted there would be an
end of the present difficulty; for if a sufficient number of individuals
were thus simultaneo