SELECTION: ORGANIC AND SOCIAL 209 



time, there is evidence, in some cases, that certain 

 males are left out in the cold unmated, and that 

 these are inferior in attractiveness or in stimulating 

 power. 



(c) While the cases of preferential mating which 

 Darwin rehed on, for instance aniong birds and 

 butterflies, require further study in the Hght of 

 criticism, there is no doubt that in many cases the 

 males exert themselves to display their special 

 quaUties. Thus Prof, and Mrs. Peckham have 

 described, in spiders of the family Attidse, the extra- 

 ordinary dances of the males before the females. 

 That the female Uterally chooses the handsomest 

 dancer remains unproved, yet it is well known 

 that she often punishes a suitor who does not 

 adequately please her by killing him there and 

 then. 



{d) In many cases, e.g. the antlers of stags, 

 there is a very intimate correlation between the 

 reproductive organs and the development of the 

 secondary sex characters. It seems that an internal 

 secretion from the reproductive organs is neces- 

 sary to start the development of certain secondary 

 sex characters. There is also evidence that the 

 secondary differences between males and females 

 hang together physiologically, being manifold out- 

 crops of the deep constitutional difference which 

 makes of one animal an egg-producer and of another 

 a sperm-producer. But this kind of inquiry, still 

 very incipient, is at a level deeper than that of 

 sexual selection, which does not touch the question 

 of origins. 



(e) It is now generally believed that what the 

 female chooses is not so much slight improvements 

 in chirping or song, slight excellences in colour 



14 



