PREFACE 
Vll 
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 cor¬ 
related 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. YIII-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. XIY); and (7) a new argument as to 
the nature and origin of the moral and intellectual faculties 
of man (Chap. XY). 
Although I maintain, and even enforce, my differences 
from some of Darwin’s views, my whole work tends forcibly 
to illustrate the overwhelming importance of Natural Selec¬ 
tion over all other agencies in the production of new species. 
