Even in using these terms he undoubtedly
afforded grounds for the objection above made, that such small and
slight variations could be of no real use, and would not determine the
survival of the individuals possessing them. We have seen, however, in
our third chapter, that even Darwin's terms were hardly justified; and
that the variability of many important species is of considerable
amount, and may very often be properly described as large. As this is
found to be the case both in animals and plants, and in all their chief
groups and subdivisions, and also to apply to all the separate parts and
organs that have been compared, we must take it as proved that the
average _amount_ of variability presents no difficulty whatever in the
way of the action of natural selection. It may be here mentioned that,
up to the time of the preparation of the last edition of _The Origin of
Species_, Darwin had not seen the work of Mr. J.A. Allen of Harvard
University (then only just published), which gave us the first body of
accurate comparisons and measurements demonstrating this large amount of
variability.
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