CHAPTER XVIII. SECONDARY SEXUAL CHARACTERS OF MAMMALS, continued. Voice—Remarkable sexual peculiarities in seals—Odour—Development of the hair—Colour of the hair and skin—Anomalous case of the female being more ornamented than the male—Colour and ornaments due to sexual selection—Colour acquired for the sake of protection—Colour, though common to both sexes, often due to sexual selection—On the disappearance of spots and stripes in adult quadrupeds—On the colours and ornaments of the Quadrumana—Summary. PART III. SEXUAL SELECTION IN RELATION TO MAN, AND CONCLUSION. CHAPTER XIX. SECONDARY SEXUAL CHARACTERS OF MAN. Differences between man and woman—Causes of such differences, and of certain characters common to both sexes—Law of battle—Differences in mental powers, and voice—On the influence of beauty in determining the marriages of mankind—Attention paid by savages to ornaments—Their ideas of beauty in women—The tendency to exaggerate each natural peculiarity. CHAPTER XX. SECONDARY SEXUAL CHARACTERS OF MAN, continued. On the effects of the continued selection of women according to a different standard of beauty in each race—On the causes which interfere with sexual selection in civilised and savage nations—Conditions favourable to sexual selection during primeval times—On the manner of action of sexual selection with mankind—On the women in savage tribes having some power to choose their husbands—Absence of hair on the body, and development of the beard—Colour of the skin—Summary. CHAPTER XXI. GENERAL A SUMMARY AND CONCLUSION. Main conclusion that man is descended from some lower form—Manner of development—Genealogy of man—Intellectual and moral faculties—Sexual selection—Concluding remarks. THE DESCENT OF MAN; AND SELECTION IN RELATION TO SEX. INTRODUCTION.