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THE AMERICAN NATURALIST [Vol. LIII 



(2) they are the result of natural selection, acting on 

 congenital tendencies toward such movements as proved 

 to be adaptive. 



Without discussing the merits of these rival theories, 

 which are by no means mutually exclusive, I merely wish 

 to point out that both of them assume a complete contin- 

 gency as regards the relation of means to end. On the 

 assumption that instinct is inherited habit, the actions, 

 before becoming habitual, must have been performed 

 either intelligently or as a result of blind groping. In 

 either case, their adaptedness to the end in view was, at 

 the outset, accidental, as we have already seen. On the 

 assumption that instincts have arisen through natural 

 selection, chance tendencies toward movements of an 

 adaptive sort were perpetuated. Here, the complete 

 contingency is obvious, unless we assume some directing 

 influence determining the nature of the variations. I 

 shall return to this last point later. 



Still lower than instincts, in the scale of organic beha- 

 \ i()r, we have the various responses to stimuli which are 

 known as "tr()])isnis " or "taxes." lender this head are 

 included the loconiot ion of the oi-u'aiiism to or from a 

 source of stinml.Mt i.)n. or. in the case of a Hxed organism, 

 the assumption of a (Ictinitc i)osi1i<)n, or tlie arrangement 

 of its parts, with relation to the direction of the stimulus. 



Here, again, we have two rival hypotheses, wliich are 

 not, it seems to me, wholly antagonistic. According to 

 one view, the organisms are "fatally" turned to or from 

 the source of light, heat, or the like by the unecpial stimu- 

 lation of the opposite sides of the body. When the ap- 

 ])ropriate orientation lias })een brought {d)out, the two 

 >i.h- (.f the oruanisiu an- <M,ually an\'ct<Ml and further 

 locoinolioii wil! he ill line with the sunrcc of stinndation. 



Th- oih< r virw ia>> -liv>^ ..n iho>r ('a>('> In which or- 



stiniuhi-. l)nl nmhTuo i-an(h»m movements, having no 

 p!-inia!-\ i-ch-itidii lo it. in what are regarded as the most 

 priHiiti\e cases the stimulns which results in a change 



