GENERAL SUMMARY AND CONCLUSION 705 



many generations for the more highly ornamented males; 

 the esthetic capacity of the females having been advanced 

 through exercise or habit just as our own taste is gradually 

 improved. In the male, through the fortunate chance of a 

 few feathers being left unchanged, we can distinctly trace 

 how simple spots with a little fulvous shading on one side 

 may have been developed by small steps into the wonderful 

 ball-and-socket ornaments; and it is probable that they 

 were actually thus developed. 



Every one who admits the principle of evolution, and 

 yet feels great difficulty in admitting that female mammals, 

 birds, reptiles and fish, could have acquired the high taste 

 implied by the beauty of the males, and which generally 

 coincides with our own standard, should reflect that the 

 nerve -cells of the brain in the highest as well as in the 

 lowest members of the Vertebrate series, are derived from 

 those of the common progenitor of this great kingdom. 

 For we can thus see how it has come to pass that certain 

 mental faculties, in various and widely distinct groups of 

 animals, have been developed in nearly the same manner 

 and to nearly the same degree. 



The reader who has taken the trouble to go through the 

 several cnapters devoted to sexual selection will be able to 

 judge how far the conclusions at which I have arrived are 

 supported by sufficient evidence. If he accepts these con 

 elusions he may, I think, safely extend them to mankind; 

 but it would be superfluous here to repeat what I have so 

 lately said on the manner in which sexual selection appar- 

 ently has acted on man, both on the male and female side, 

 causing the two sexes to differ in body and mind, and the 

 several races to differ from each other in various characters, 

 as well as from their ancient and lowly organized pro- 

 genitors. 



He who admits the principle of sexual selection will be 

 led to the remarkable conclusion that the nervous system 

 not only regulates most of the existing functions of the 

 body, but has indirectly influenced the progressive develop- 

 ment of various bodily structures and of certain menta} 

 qualities. Courage, pugnacity, perseverance, strength an(^ 

 size of body, weapons of all kinds, musical organs, both\ 

 vocal and instrumental, bright colors and ornamental ap- 

 pendages, have all been indirectly gained by the one sex or 

 the other, through the exertion of choice, the influence of 



