582 THE DESCENT OF MAN 



manage her tail during incubation; but it is now known* 

 that she "enters the nest head first, and then turns round 

 with her tail sometimes over her back, but more often bent 

 round by her side. Thus in time the tail becomes quite 

 askew, and is a tolerable guide to the length of time the 

 bird has been sitting." Both sexes of an Australian king- 

 fisher (^Tanysiptera sylvia) have the middle tail-feathers 

 greatly lengthened, and the female makes her nest in a 

 hole; and, as I am informed by Mr. E. B. Sharpe, these 

 feathers become much crumpled during incubation. 



In these two latter cases the great length of the tail- 

 feathers must be in some degree inconvenient to the female; 

 and, as in both species the tail-feathers of the female are 

 somewhat shorter thaa those of the male, it might be argued 

 that their full development had been prevented through 

 natural selection. But if the development of the tail of the 

 peahen had been checked only when it became inconven- 

 iently or dangerously great, she would have retained a much 

 longer tail than she actually possesses; for her tail is not 

 nearly so long, relatively to the size of her body, as that of 

 many female pheasants, nor longer than that of the female 

 turkey. It must also be borne in mind that, in accordance 

 with this view, as soon as the tail of the peahen became 

 dangerously long, and its development was consequently 

 checked, she would have continually reacted on her male 

 progeny, and thus have prevented the peacock from acquir- 

 ing his present magnificent train. We may therefore infer 

 that the length of the tail in the peacock and its shortness 

 in the peahen are the result of the requisite variations in 

 the male having been from the first transmitted to the male 

 offspring alone. 



We are led to a nearly similar conclusion with respect 

 to the length of the tail in the various species of pheasants. 

 In the Eared pheasant {^Grossoptilon auritum) the tail is of 

 equal length in both sexes, namely, sixteen or seventeen 



8 Mr. Eamsay, in "Proe. Zoolog. Soc," 1868, p. 50. 



