I have also made what appears to me an important change in the
arrangement of the subject. Instead of treating first the comparatively
difficult and unfamiliar details of variation, I commence with the
Struggle for Existence, which is really the fundamental phenomenon on
which natural selection depends, while the particular facts which
illustrate it are comparatively familiar and very interesting. It has
the further advantage that, after discussing variation and the effects
of artificial selection, we proceed at once to explain how natural
selection acts.

Among the subjects of novelty or interest discussed in this volume, and
which have important bearings on the theory of natural selection, are:
(1) A proof that all _specific_ characters are (or once have been)
either useful in themselves or correlated with useful characters (Chap.
VI); (2) a proof that natural selection can, in certain cases, increase
the sterility of crosses (Chap. VII); (3) a fuller discussion of the
colour relations of animals, with additional facts and arguments on the
origin of sexual differences of colour (Chaps. VIII-X); (4) an attempted
solution of the difficulty presented by the occurrence of both very
simple and very complex modes of securing the cross-fertilisation of
plants (Chap. XI); (5) some fresh facts and arguments on the
wind-carriage of seeds, and its bearing on the wide dispersal of many
arctic and alpine plants (Chap. XII); (6) some new illustrations of the
non-heredity of acquired characters, and a proof that the effects of use
and disuse, even if inherited, must be overpowered by natural selection
(Chap. XIV); and (7) a new argument as to the nature and origin of the
moral and intellectual faculties of man (Chap. XV).

* * * * *