142 
DARWINISM 
CHAP. 
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 dis¬ 
tinguish each species from its nearest allies—are entirely un- 
adaptive, 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 con¬ 
stitute any of the more dominant species. 1 
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 Cf. J. Romanes has adduced 
1 Darwin’s latest expression of opinion on this question is interesting, since 
it shows that he was inclined to return to his earlier view of the general, or 
universal, utility of specific characters. In a letter to Semper (30th Nov. 
1878) he writes: “As our knowledge advances, very slight differences, con¬ 
sidered by systematists as of no importance in structure, are continually 
found to be functionally important ; and I have been especially struck with 
this fact in the case of plants, to which my observations have, of late years, 
been confined. Therefore it seems to me rather rash to consider slight 
differences between representative species, for instance, those inhabiting the 
different islands of the same archipelago, as of no functional importance, and 
as not in any way due to natural selection ” (Life of Darwin, vol. iii. p. 161). 
