THE SEXES AND SEXUAL SELECTION. 5 



some cases at least to be truly part and parcel with the male or 

 female constitution, they are only of secondary importance in 

 the reproductive process. The beard of man and the mane 

 of the lion, the antlers of stags and the tusks of elephants, the 

 gorgeous plumage of the peacock or of the bird of paradise, 

 are familiar examples of secondary sexual characters in males. 

 Nor are the females lacking in special characteristics, which 

 serve as indices of their true nature. Large size is one of the 

 commonest of these ; while in some few cases the excellencies 

 of colour, and other adornments, are possessed by the females 

 rather than by their mates. 



The whole subject of secondary sexual characters has found 

 its most extensive treatment in Darwin's "Descent of Man," 

 and to that work, therefore, the more so as its limits exceed 

 those of the present volume, the reader must be assumed to 

 make reference. All that can be here attempted is an illustra- 

 tion, by representative cases, of the main differences between 

 the sexes ; from which we shall pass to Darwin's interpretation, 

 and, after a fresh survey, to the explanation by which we propose 

 to supplement his theory. 



§ 2. Illustrations from Darivin. ■ — • Among invertebrates, 

 prominent secondary sexual characters are rarely exhibited 

 outside the great division of jointed-footed animals or arthro- 

 pods. There, however, among crustaceans and spiders, but 

 especially among insects, beautiful illustrations abound. Thus 

 the great claws of crabs are frequently much larger in the 

 males; and male spiders often differ from their fiercely coy 

 mates, in smaller size, darker colours, and sometimes in the 



Winged Male and Wingless Female of a certain Moth 

 {Orgyia antiqud). — From Leunis. 



power of producing rasping sounds. Among insects, the males 

 are frequently distinguished by brighter colours attractively dis- 

 played, by weapons utilised in disposing of their rivals, and 

 by the exclusive possession of the power of noisy love-calling. 

 Thus, as the Greek observed, the cicadas "live happy, having 

 voiceless wives." Not a few male butterflies are pre-eminently 



