Utilising this information we will now endeavour to give some
idea of the nature and extent of variation in the species of animals and
plants.
It is very commonly objected that the widespread and constant
variability which is admitted to be a characteristic of domesticated
animals and cultivated plants is largely due to the unnatural conditions
of their existence, and that we have no proof of any corresponding
amount of variation occurring in a state of nature. Wild animals and
plants, it is said, are usually stable, and when variations occur these
are alleged to be small in amount and to affect superficial characters
only; or if larger and more important, to occur so rarely as not to
afford any aid in the supposed formation of new species.
This objection, as will be shown, is utterly unfounded; but as it is one
which goes to the very root of the problem, it is necessary to enter at
some length into the various proofs of variation in a state of nature.
This is the more necessary because the materials collected by Mr. Darwin
bearing on this question have never been published, and comparatively
few of them have been cited in _The Origin of Species_; while a
considerable body of facts has been made known since the publication of
the last edition of that work.
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