66). And again, after speaking of changed conditions
"affording a better chance of the occurrence of favourable variations,"
he adds: "_Unless such occur natural selection can do nothing_"
(_Origin_, p. 64). These expressions are hardly consistent with the fact
of the constant and large amount of variation, of every part, in all
directions, which evidently occurs in each generation of all the more
abundant species, and which must afford an ample supply of favourable
variations whenever required; and they have been seized upon and
exaggerated by some writers as proofs of the extreme difficulties in the
way of the theory. It is to show that such difficulties do not exist,
and in the full conviction that an adequate knowledge of the facts of
variation affords the only sure foundation for the Darwinian theory of
the origin of species, that this chapter has been written.
FOOTNOTES:
[Footnote 16: _Foraminifera_, preface, p. x.]
[Footnote 17: _United States Geological Survey of the Territories_,
1874.]
[Footnote 18: _Proceedings of the Entomological Society of London_,
1875, p.
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