usly and similarly modified, there need be no longer
any danger of the variety becoming swamped by intercrossing." I must
again refer my readers to my third chapter for the proof that such
simultaneous variability is not an assumption but a fact; but, even
admitting this to be proved, the problem is not altogether solved, and
there is so much misconception regarding variation, and the actual
process of the origin of new species is so obscure, that some further
discussion and elucidation of the subject are desirable.

In one of the preliminary chapters of Mr. Seebohm's recent work on the
_Charadriidae_, he discusses the differentiation of species; and he
expresses a rather widespread view among naturalists when, speaking of
the swamping effects of intercrossing, he adds: "This is unquestionably
a very grave difficulty, to my mind an absolutely fatal one, to the
theory of accidental variation." And in another passage he says: "The
simultaneous appearance, and its repetition in successive generations,
of a beneficial variation, in a large number of individuals in the same
locality, cannot possibly be ascribed to chance." These remarks appear
to me to exhibit an entire misconception of the facts of variation as
they actually occur, and as they have been utilised by natural selection
in the modification of species. I have already shown that every part of
the organism, in common species, does vary to a very considerable
amount, in a large number of individuals, and in the same locality; the
only point that remains to be discussed is, whether any or most of these
variations are "beneficial." But every one of these variations consists
either in increase or diminution of size or power of the organ or
faculty that varies; they can all be divided into a more effective and a
less effective group--that is, into one that is more beneficial or less
beneficial. If less size of body would be beneficial, then, as half the
variations in size are above and half below the mean or existing
standard of the species, there would be ample beneficial variations; if
a darker colour or a longer beak or wing were required, there are always
a considerable number of individuals darker and lighter in colour than
the average, with longer or with shorter beaks and wings, and thus the
beneficial variation must always be present. And so with every other
part, organ, function, or habit; because, as variation, so far as we
know, is and always must be in the t