Tlie Evidence from Sexual Characters. 203 



In the cases where the females of allied species do dif- 

 fer the difference is rarely so great as between the males. 

 Darwin says : "We see this clearly in the whole family 

 of the Gallinaceae : the females for instance of the com- 

 mon and Japan pheasant, and especially of the gold and 

 Amherst pheasant, of the silver pheasant and the wild 

 fowl, resemble each other very closely in color, while the 

 males differ to an extraordinary degree. So it is with 

 the Cotingidae Fringillidae and many other families. 

 There can indeed be no doubt that as a general rule the 

 females have been modified to a less extent than the 

 males." (Variation, Vol. II. p. 184) 



As* regards the relation between the young and the 

 adult, the general rule is that when the sexes differ the 

 young of both sexes in their first plumage resemble the 

 adult female as they do in the common fowl or the pea- 

 cock, or else they resemble her more closely than they do 

 the adult male. 



Darwin says that innumerable instances of this law 

 could be given in all orders, but that it will suffice to 

 call to mind the common pheasant, duck, and house 

 sparrow. 



There are a few cases in which the young male is like 

 the adult male, and the young female like the adult fe- 

 male, and there are also a few cases where the young of 

 both sexes resemble the adult male, but the difference be- 

 tween the sexes is never, in this case, very great, and in 

 stances are so rare that Darwin, who says that he has re- 

 corded all he could find, gives only nine. In his summary 

 he says : " We thus see that the cases in which female 

 birds are more conspicuously colored than the males, with 

 the young in their immature plumage resembling the 

 adult males instead of the adult females, are not numer- 

 ous, though they are distributed in various orders. The 



