Darwin contended, disuse can so far reduce
an organ as to render it rudimentary, and in many cases get rid of
it altogether, why cannot use create as much as disuse can destroy,
provided it has anything, no matter how low in structure, to begin
with? Let us know where we stand. If it is admitted that use and
disuse can do a good deal, what does a good deal mean? And what is
the proportion between the shares attributable to use and disuse and
to natural selection respectively? If we cannot be told with
absolute precision, let us at any rate have something more definite
than the statement that natural selection is "the most important
means of modification."
Mr. Darwin gave us no help in this respect; and worse than this, he
contradicted himself so flatly as to show that he had very little
definite idea upon the subject at all. Thus in respect to the
winglessness of the Madeira beetles he wrote:--
"In some cases we might easily put down to disuse modifications of
structure, which are wholly or mainly due to natural selection.
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