60 PECKHAM. [Vol. 1. 



females pay close attention to the love dances of the males, and 

 also that they have not only the power, but the will, to exercise 

 a choice among the suitors for their favor. 



Second : The fact that every male bird finds a mate 

 " would almost or quite neutralize any effect of sexual selection 

 of color or ornament ; since the less highly colored birds would 

 be at no disadvantage as regards leaving healthy offspring." 

 In spiders, as the females gradually become adult, they have a 

 choice from among a number of males, as these mature several 

 days earlier. The males will pair as often as they have the 

 opportunity and as the mating season lasts for two or three weeks 

 the more brilliant males may easily be selected again and again. 



The fact that in the AUidse the males vie with each other 

 in making an elaborate display, not only of their grace and 

 agility but also of their beauty, before the females, and that the 

 females, after attentively watching the dances and tournaments 

 which have been executed for their gratification, select for their 

 mates the males that they find most pleasing, points strongly to 

 the conclusion that the great differences in color and in orna- 

 ment between the males and females of these spiders are the 

 result of sexual selection. 



Note. — Since finishing tlie above we have seen, in the February 

 number of the Popular Science Monthly, T. H. Morgan's article on 

 The Dance of the Lady Crab. The observation therein noted is full of 

 interest, showing, as it does, that sexual display in the invertebrates i s 

 not confined to spiders. 



