THE SEXES AND SEXUAL SELECTION. 



attempted is an illustration, by representative cases, of the main differ- 

 ences between the sexes; from which we shall pass to Darwin's inter- 

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

 propose to supplement his theory. 



II. Illustrations from Darwin. — Among invertebrates, prom- 

 inent secondary sexual characters are rarely exhibited outside the 

 great division of jointed-footed animals or arthropods. There, how- 

 ever, 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 colors, and some- 

 times in the power of producing rasping sounds. Among insects, the 

 males are frequently distinguished by brighter colors attractively dis- 

 played, by weapons utilized 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 

 preeminently more brilliant than 

 the females; and many male 



beetles fight Savagely for the F ' G ' -Wing^M aIe and Wingless Female of a 

 ° ° J certain Moth (Orgyta antiqua). — from Leunis. 



possession of their mates. 



Passing to backboned animals, we find that among fishes the males 

 are frequently distinguished by bright colors and ornamental append- 

 ages, as well as by structural adaptations for combat. Thus the 

 " gemmeous dragonet " {Callionymus lyrd) is flushed with gorgeous 

 color, in great contrast to the " sordid " female, and is further adorned 

 by a graceful elongation of the dorsal fin. In many cases, as in the 

 sea-scorpion (Cottus scorpius), or in the stickleback (Gasterosteus) , it 

 is only at the reproductive period that the males are thus transformed, 

 literally putting on a wedding-garment. Every one knows, on the 

 other hand, the hooked lower jaw of the male salmon, which comes to 

 be of use in the furious charges between rivals; and this is but one 

 illustration of many structures utilized in the battle for mates. In 

 regard to amphibians, it is enough to recall the notched crests and 

 lurid coloring of our male newts, and the indefatigable serenading 

 powers of male frogs and toads, to which the females are but weakly 

 responsive. Among reptiles, differences of this sort are comparatively 

 rare, but male snakes have often more strongly-pronounced tints, and 

 the scent-glands become more active during the breeding season. In 

 this, as in many other cases, love has its noisy prayer replaced by the 

 silent appeal of fragrant incense. Among lizards, the males are often 

 more brightly decorated, the splendor of their colors being frequently 



