THE EVOLUTION OF SEX. 



exaggerated at pairing-time. They may be further distinguished by 

 crests and wattlelike pouches; while horns, probably used in fighting, 

 are borne by some male chameleons. 



It is among birds, however, that the organic apparatus of courtship 

 is most elaborate. The males very generally excel in brighter colors 

 and ornaments. Beautiful plumes, elongated feathery tresses, brightly- 

 colored combs and wattles, topknots, and curious markings, occur 

 with marvelous richness of variety. These are frequently displayed by 

 their proud possessers before the eyes of their desired mates, with 

 mingled emotions of eager love and pompous vanity; or it may be to 

 the subtler charms of music that the wooers mainly trust. During the 



Fig. 



•Male and Female Blackcocks. 



breeding season, the males are jealously excited and pugnacious, while 

 some have special weapons for dealing directly with their rivals. The 

 differences between the magnificent male birds-of-paradise and their 

 sober mates, between the peacock with his hundred eyes and the plain 

 peahen, between the musical powers of male and female songsters, are 

 very familiar facts. Or again, the combs and "gills" of cocks, the 

 "wattles" of turkey-cocks, the immense topknot of the male 

 umbrella-bird {Cephalopterus omatiis), the throat-pouch of the 

 bustard, — illustrate another series of secondary sexual characters. 

 The spurs of cocks and allied birds are the most familiar illustrations 

 of weapons used by the males in fighting with rivals. As in other 

 animals, it is important to notice that male birds often acquire their 

 special secondary characters — such as color, markings, and special 

 forms of feathers — only as they approach sexual maturity, and some- 

 times retain them in all their glory only during the breeding season. 



