196 SEXUAL SELECTION : BIRDS. [Part II. 



pugnacious disposition ; and her wattles then become en- 

 larged and more brilliantly colored. So, again, the female 

 of one of the emus (Dromoeus irroratus) is considerably 

 larger than the male, and she possesses a slight top-knot, 

 but is otherwise undistinguishable in plumage. She ap- 

 pears, however, " to have greater power, when angry or 

 otherwise excited, of erecting, like a turkey-cock, the 

 feathers of her neck and breast. She is usually the more 

 courageous and pugilistic. She makes a deep, hollow, gut- 

 tural boom, especially at night, sounding like a small 

 gong. The male has a slenderer frame and is more docile, 

 with no voice beyond a suppressed hiss when angry, or a 

 croak." He not only performs the whole duty of incuba- 

 tion, but has to defend the young from their mother ; " for 

 as soon as she catches sight of her progeny she becomes 

 violently agitated, and notwithstanding the resistance of 

 the father appears to use her utmost endeavors to destroy 

 them. For months afterward it is unsafe to put the par- 

 ents together, violent quarrels being the inevitable result, 

 in which the female generally comes off conqueror." 23 So 

 that with this emu we. have a complete reversal not only 

 of the parental and incubating instincts, but of the usual 

 moral qualities of the two sexes ; the females being sav- 

 age, quarrelsome, and noisy, the males gentle and good. 

 The case is very different with the African ostrich, for the 

 male is somewhat larger than the female and has finer 

 plumes with more strongly-contrasted colors ; neverthe- 

 less, he undertakes the whole duty of incubation. 24 



I will specify the few other cases known to me, in 

 which the female is more conspicuously colored than the 

 male, although nothing is known about their manner of 



M See the excellent account of the habits of this bird under confine- 

 ment, by Mr- A. W. Bennett, in 'Land and Water,' May, 18G8, p. 233. 



84 Mr. Sclater. on the incubation of the Struthiones, ' Proc. Zool. Soc.,' 

 June 9, 1863. 



