MENTAL AND SOCIAL EVOLUTION 123 



proportion to its entire brain. This knowledge is impor- 

 tant to the fisherman, casting the fly in the trout stream. 

 For, if the trout gets a sight of him, before it is hooked, 

 it escapes ; and after a good sized trout is hooked, upon 

 delicate tackle, a good fisherman will not move a muscle, 

 except that necessary to operate the reel. The motion of 

 a finger will sometimes cause the trout to make remark- 

 able struggles to relieve himself of the hook. No one 

 attributes these traits of the trout to any other cause, 

 than that of his nervous system. Then, why should the 

 behavior of man be attributed to any other cause than 

 the control his brain is shown to have over his motor 

 muscles ? 



Mental traits are inherited, because they depend, 

 upon the peculiar structure of the brain, and structure 

 is inherited. Aptitude and genius often run in fam- 

 ilies ; so does insanity. Every breeder of animals knows 

 how temperaments, and tendencies, peculiarities of 

 behavior, are handed down from generation to genera- 

 tion. This is so, because the peculiar structure of the 

 brain is inheritable, and the brain controls .the behavior 

 of both man and animals. Natural selection as said 

 before, does not confine its operation to physical traits, 

 anymore than it does to mental traits in animals. Man, 

 the weakest of animals, is the best adapted, and there- 

 fore dominates, and survives all others, as a class, be- 

 cause of his mental power, to contrive, construct, to 

 manufacture, and to farm the soil. He annihilates 

 other animals, selecting those best suited to his needs 

 for domestication. Other animals are selected, by this 

 law of survival, on account of their superior mental 

 traits, by which they overcome their enemies by cunning 

 and subterfuge. Beside, the "minds" of animals have 

 been evolved by domesticating them. The dog, the 



