658 



THE POPULAR SCIENCE MONTHLY. 



I have given, thus far, only a few very conspicuous examples of in- 

 stinct, in order the more clearly to contrast this faculty wiih intelli- 

 gence. I might have added many other conspicuous and well recog- 

 nized examples, such as the migrations and nest-making of birds, the 

 dam-building of beavers, etc. But we would have a very imperfect no- 

 tion of tlie wideness of the operation of instinct if we confined ourselves 

 to these conspicuous cases. Instinct in a less remarkable degree is uni- 

 versal among animals, including man himself. But what is universal 

 in the popular mind creates no surprise, attracts no attention, and 

 seems to need no explanation ; yet it is these very universal and there- 

 fore unobserved phenomena which are the most instructive to science. 

 Not only the action of bees and ants and wasps, not only the migra- 

 tions and the nest-makins: of birds and the dam-buildincj of beavers, 

 must be accredited to instinct, but also all complex voluntary motions 

 lohich are performed loithout experience. Such, for example, in many 

 animals are the acts of running, swimming, flying, walking, and stand- 

 ing, etc. Yes, even the simple act of standing or walking is really a 

 marvelous feat in balancing I'equiring the nice adjustment and 

 perfect coordination of perhaps a hundred different muscles. Even 

 the simple voluntary act of sight (looking) requires the most exquisite 

 adjustment of the optic axes, the lenses, and the iris. These complex 

 actions are acquired by us by experience., though there is doubtless 

 also, evey% in i<s, a large inherited element, an inherited capacity by 

 which we acquire them with comparative facility. But the new-born 

 ruminant quadruped or gallinaceous bird stands and walks and uses 

 the eyes at once, icithout experience. The power to coordinate these 

 muscles, and to accomplish these complex and difficult actions, is 

 wholly inherited, not acquired.' 



Man. 



Vertebrates. 



MOLLUSKS. 



Radiates. 



Thus defined, intelligence and instinct are not mutually exclusive, 

 as some seem to suppose : the one is not simply a characteristic of man 

 and the other of animals, but they coexist in varying relative propor- 

 tions throughout the animal kingdom. As a broad general fact, in 

 going down the animal scale we find that instinct varies inversely 

 as intelligence.^ The accompanying diagram expresses in a general 

 way this relation. If the line a h represents the animal scale from 



' " Instinct in New-bom Chickens." Naturalist, vol. vii., pp. 300, 377, 384. 

 ^ As we are not dealing here with measurable quantities, of course I do not use the 

 expression " varies inversely as " in a strict mathematical sense. 



