The theory of protective colouration has been carried to absurd lengths—It will not bear close scrutiny—Cryptic colouring—Sematic colours—Pseudo-sematic colours—Batesian and Müllerian mimicry—Conditions necessary for mimicry—Examples—Recognition markings—The theory of obliterative colouration—Criticism of the theory—Objections to the theory of cryptic colouring—Whiteness of the Arctic fauna is exaggerated—Illustrative tables—Pelagic organisms—Objectors to the Neo-Darwinian theories of colouration are to be found among field naturalists—G. A. B. Dewar, Gadow, Robinson, F. C. Selous quoted—Colours of birds’ eggs—Warning colouration—Objections to the theory—Eisig’s theory—So-called intimidating attitudes of animals—Mimicry—The case for the theory—The case against the theory—“False mimicry”—Theory of recognition colours—The theory refuted—Colours of flowers and fruits—Neo-Darwinian explanations—Objections—Kay Robinson’s theory—Conclusion that Neo-Darwinian theories are untenable—Some suggestions regarding the colouration of animals—Through the diversity of colouring of organisms something like order runs—The connection between biological molecules and colour—Tylor on colour patterns in animals—Bonhote’s theory of pœcilomeres—Summary of conclusions arrived at. CHAPTER VII 297 Sexual Dimorphism Meaning of the term—Fatal to Wallaceism—Sexual Selection—The law of battle—Female preference—Mutual Selection—Finn’s experiments—Objections to the theory of Sexual Selection—Wallace’s explanation of sexual dimorphism stated and shown to be unsatisfactory—The explanation of Thomson and Geddes shown to be inadequate—Stolzmann’s theory stated and criticised—Neo-Lamarckian explanation of sexual dimorphism stated and criticised—Some features of sexual dimorphism—Dissimilarity of the sexes probably arises as a sudden mutation—The four kinds of mutations—Sexual dimorphism having shown itself, Natural Selection determines whether or not the organisms which display it shall survive. CHAPTER VIII 345 The Factors of Evolution