SEX UAL SELECTION. 255 



two sexes of the same species appear to have been differ- 

 ently affected; in the Agelceus phwniceus the males have 

 had their colors greatly intensified in the south; whereas 

 with Cardinalis virginianus it is the females which have 

 been thus affected; with Quiscalus major the females have 

 been rendered extremely variable in tint, while the males 

 remain nearly uniform.* 



A few exceptional cases occur in various classes of ani- 

 mals, in which the females instead of the males have 

 acquired well-pronounced secondary sexual characters, such 

 as brighter colors, greater size, strength or pugnacity. 

 With birds there has sometimes been a complete transposi- 

 tion of the ordinary characters proper to each sex; the 

 females having become the more eager in courtship, the 

 males remaining comparatively passive, but apparently 

 selecting the more attractive females, as we may infer from 

 the results. Certain hen birds have thus been rendered 

 more highly colored or otherwise ornamented, as well as 

 more powerful and pugnacious than the cocks ; these 

 characters being transmitted to the female offspring alone. 



It may be suggested that in some cases a double process 

 of selection has been carried on; that the males have selected 

 the more attractive females and the latter the more attract- 

 ive males. This, process, however, though it might lead 

 to the modification of both sexes, would not make the one 

 sex different from the other, unless indeed their tastes for 

 the beautiful differed; but this is a supposition too improba- 

 ble to be worth considering in the case of any animal, except- 

 ing man. There are, however, many animals in which the 

 sexes resemble each other, both being furnished with the 

 same ornaments, which analogy would lead us to attribute 

 to the agency of sexual selection. In such cases it may be 

 suggested with more plausibility that there has been a 

 double or mutual process of sexual selection; the more 

 vigorous and precocious females selecting the more 

 attractive and vigorous males, the latter rejecting all 

 except the more attractive females. But from what we 

 know of the habits of animals, this view is hardly probable, 

 for the male is generally eager to pair with any female. It 

 is more probable that the ornaments common to both sexes 

 were acquired by one sex, generally the male, and then 



* "Mammals and Birds of E. Florida," pp. 234, 280, 295. 



