PREFACE vil 



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 mth 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 difierences 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. XIV) ; and (7) a new argument as to 

 the nature and origin of the moral and intellectual faculties 

 of man (Chap. XV). 



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. 



