353 The Descent of Man. Part IT. 



the males alone of Sitana possess a throat-pouch ; and this is 

 splendidly tinted with blue, black, and red. In the 1'roctotretus 

 tenuis of Chile the male alone is marked with spots of blue, 

 green, and coppery-red. 71 In many cases the males retain the 

 same colours throughout the year, but in others they become 

 much brighter during the breeding-season ; I may give as an 

 additional instance the Calotes maria, which at this season has a 

 bright red head, the rest of the body being green. 72 



Both sexes of many species are beautifully coloured exactly 

 alike ; and there is no reason to suppose that such colours are 

 protective. No doubt with the bright green kinds which live 

 in the midst of vegetation, this colour serves to conceal them , 

 and in N. Patagonia I saw a lizard {Proctotretus multimaculatus) 

 which, when frightened, flattened its body, closed its eyes, and 

 then from its mottled tints was hardly distinguishable from the 

 surrounding sand. But the bright colours with which so many 

 lizards are ornamented, as well as their various curious appen- 

 dages, were probably acquired by the males as an attraction, 

 and then transmitted either to their male offspring alone, or to 

 both sexes. Sexual selection, indeed, seems to have played 

 almost as important a part with reptiles as with birds ; and the 

 less conspicuous colours of the females in comparison with the 

 males cannot be accounted for, as Mr. Wallace believes to be the 

 case with birds, by the greater exposure of the females to danger 

 during incubation. 



CHAPTER XIII. 

 Secondary Sexual Characters of Biri s. 



Fexual differences — Law of battle — Special weapons — Vocal organs — 

 Instrumental music — Love-antics and dances — Decorations, permanent 

 and seasonal — Double and single annual moults — Display of ornaments 

 by the males. 



Secondary sexual characters are more diversified and con- 

 spicuous in birds, though not perhaps entailing more important 

 changes of structure, than in any other class of animals. I shall, 

 therefore, treat the subject at considerable length. Male birds 

 sometimes, though rarely, possess special weapons for fighting 



71 For Proctotretus see ' Zoology the Indian Calotes, see ' Reptiles of 



of the Voyage of the "Beagle:" British India,' by Dr. Gunther, p. 



Reptiles,' by Mr. Bell. p. 8. For 143. 



the Lizards of S. Atrica, see ' Zoology 72 Gunther in ' Proc. Zoolog. Soc' 



of S. Africa: Keptiies,' by Sir 1870, p. 778, with a coloured 



Andrew Smith, pi. L5 and 39. For figure. 



