SEXUAL SELECTION 



615 



ascertained, by examining many specimens, that the trachea 

 is not convoluted in either sex of R, hengalensis, which spe- 

 cies resembles B. australis so closely that it can hardly be 

 distinguishd except by its shorter toes. This fact is an- 

 other striking instance of the law that secondary sexual 



Fio. 62.— Ehynchsea oapensis (from Brehm). 



characters are often widely different in closely allied 

 forms, though it is a very rare circumstance when such 

 differences relate to the female sex. The young of both 

 sexes of B. hengalensis in their first plumage are said to 

 resemble the mature male." There is also reason to be- 

 lieve that the male undertakes the duty of incubation, for 



w "The Indian Field," Sept. 1858. p, 3. 



