ability to "conceive any means" by which acquired
characters impress themselves on the reproductive
elements, is no adequate reason for assuming that
they cannot do this.

Let me add that much more simply, and still more
conclusively, may this objection raised by the neo-
Darwinists to the hypothesis of use-inheritance, be
disposed of. Huyghens rejected the theory of gravi-
tation. What was his reason? He said that such an
attraction as was implied could not be explained by
any principles of mechanics. That is to say, he could
not "conceive any means" by which the mutual in-
fluence of the attracting bodies could be effected.
Nevertheless the theory of gravitation was estab-
lished by irrefragable proofs, and has long been uni-
versally accepted.

Of course the foregoing paragraphs should form
a part of The Principles of Biology. But as, in 1899,
I issued a finally-revised edition of that work, and
see no probability that I shall ever be able to issue
another, I decide to include them here.

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