SEXUAL SELECTION 579 



in this manner when nearly mature, notwithstanding that 

 they were exposed to some additional danger, might sur- 

 vive, and, from being favored through sexual selection, 

 would procreate their kind. As a relation often exists be- 

 tween the period of variation and the form of transmission, 

 if the bright colored young males were destroyed and the 

 mature ones were successful in their courtship, the males 

 alone would acquire brilliant colors and would transmit 

 them exclusively to their male offspring. But 1 by no 

 means wish to maintain that the influence of age on the 

 form of transmission is the sole cause of the great differ- 

 ence in brilliancy between the sexes of many birds. 



"When the sexes of birds differ in color, it is interesting 

 to determine whether the males alone have been modified by 

 sexual selection, the females having been left unchanged, or 

 only partially and indirectly thus changed ; or whether the 

 females have been specially modified through natural selec- 

 tion for the sake of protection. I will, therefore, discuss 

 this question at some length, even more fully than its in- 

 trinsic importance deserves; for various curious collateral 

 points may thus be conveniently considered. 



Before we enter on the subject of color, more especially 

 in reference to Mr. "Wallace's conclusions, it may be useful 

 to discuss some other sexual differences under a similar 

 point of view. A breed of fowls formerly existed in Ger- 

 many,' in which the hens were furnished with spurs; they 

 were good layeis, but they so greatly disturbed their nests 

 with their spurs that they could not be allowed to sit on 

 their own eggs. Hence, at one time it appeared to me 

 probable that with the females of the wild Gallinacese the 

 development of spurs had been checked through natural 

 selection from the injury thus caused to their nests. This 

 seemed all the more probable, as wing-spurs, which would 

 not be injurious during incubation, are often as well de- 

 veloped in the female as in the male; though in not a few 



• Beohstein "Naturgeaoh. Deutschlands," H93, B. iii. s. 339. 



