e of these remarks cannot, I think, be disputed.
If, for instance, a bird of some kind could procure its food more easily
by having its beak curved, and if one were born with its beak strongly
curved, and which consequently flourished, nevertheless there would be
a very poor chance of this one individual perpetuating its kind to the
exclusion of the common form; but there can hardly be a doubt, judging
by what we see taking place under domestication, that this result would
follow from the preservation during many generations of a large number
of individuals with more or less strongly curved beaks, and from the
destruction of a still larger number with the straightest beaks.

It should not, however, be overlooked that certain rather strongly
marked variations, which no one would rank as mere individual
differences, frequently recur owing to a similar organisation being
similarly acted on--of which fact numerous instances could be given with
our domestic productions. In such cases, if the varying individual did
not actually transmit to its offspring its newly-acquired character, it
would undoubtedly transmit to them, as long as the existing conditions
remained the same, a still stronger tendency to vary in the same manner.
There can also be little doubt that the tendency to vary in the same
manner has often been so strong that all the individuals of the same
species have been similarly modified without the aid of any form of
selection. Or only a third, fifth, or tenth part of the individuals may
have been thus affected, of which fact several instances could be given.
Thus Graba estimates that about one-fifth of the guillemots in the Faroe
Islands consist of a variety so well marked, that it was formerly ranked
as a distinct species under the name of Uria lacrymans. In cases of this
kind, if the variation were of a beneficial nature, the original form
would soon be supplanted by the modified form, through the survival of
the fittest.

To the effects of intercrossing in eliminating variations of all kinds,
I shall have to recur; but it may be here remarked that most animals and
plants keep to their proper homes, and do not needlessly wander about;
we see this even with migratory birds, which almost always return to the
same spot. Consequently each newly-formed variety would generally be at
first local, as seems to be the common rule with varieties in a state
of nature; so that similarly modified individuals would soon exist