26 Heredity and Social Progress 



more fully developed than the mere necessi- 

 ties of life demand. The successful contest- 

 ant would be the one with the most energy, 

 and this energy would also find an outlet 

 in changes which create secondary qualities. 

 The fighting males would grow; the surplus 

 energy speeding in one direction would also 

 find exit in the other. Secondary sexual char- 

 acters are the natural expression of surplus 

 energy created by acquired characters. At 

 least they appear under improved conditions 

 or when nutrition is superabundant, and are 

 naturally associated with surplus energy. They 

 suggest a way in which surplus energy can 

 effect organic changes in harmony with well- 

 demonstrated biological laws. 



If sexual characters are natural expressions 

 of surplus energy, they give a clew as to how 

 other characters are formed. They seem not 

 to be a class by themselves, but to reflect 

 the superior vitality of males. Should any of 

 these characters prove useful, not merely in 

 contest but also in the acquisition of nutriment, 

 they would be acquired through inheritance 

 by females as well as by males, and so become 



