It is surprising that Malthus should have been needed to give him the clue, when in the Note Book of 1837 there should occur—however obscurely expressed—the following forecast1 of the importance of the survival of the fittest. "With respect to extinction, we can easily see that a variety of the ostrich (Petise2), may not be well adapted, and thus perish out; or on the other hand, like Orpheus3, being favourable, many might be produced. This requires the principle that the permanent variations produced by confined breeding and changing circumstances are continued and produce according to the adaptation of such circumstances, and therefore that death of species is a consequence (contrary to what would appear in America) of non-adaptation of circumstances.

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