106 CONTROLLED NATURAL SELECTION 



alike ; usually the male will be found 

 to be conspicuous in one or more char- 

 acters, as in song birds. 



In conclusion it may be said that many, if 

 not the majority of those characters which 

 distinguish males from females, are similar 

 to the differences found between parents and 

 young. 



Males equal females plus some other char- 

 acters, females equal young plus some char- 

 acters. In each case the added characters 

 are alike, and according to the theory serve 

 the same purpose. 



