162 BIRDS OF THE PLAINS 



This article has already attained such a length that 

 even had I complete explanations to offer I could not 

 set them forth in this place. I must content myself 

 with giving what I believe to be the key to the solution 

 of the problem. I think that there is little doubt that 

 what a bird looks for in its mate is, not beauty or brilliance 

 of plumage, but vigour and strength. If beauty is a 

 correlative character to strength, then the hen selects 

 the most beautiful of the cocks willing to mate with 

 her, not because of his beauty, but on account of his 

 strength; likewise the cock. Now there is a very 

 intimate connection between the generative cells and 

 the body cells, and the male element tends to dissipate 

 energy and the female element to conserve it. Thus it is 

 that the general tendency of the cock is to become gaily 

 coloured and to grow plumes and other ornaments, 

 while the tendency of the hen is to remain of com- 

 paratively sombre hue. 



