ADAPTATION 



199 



of behavior is usually a noxious one, loadiii"- to a backing 

 out or turning aside. When forward iiiovt'iiu'iit is re- 

 sumed, it is a matter of chance wliotlicr the organism 

 remains hi favorable surroundings or Hnds its \va>' back 

 to the unfavorable ones. If the latter, tlic "nvoidiiig 

 reaction" recurs, and the performance is rcix^atcd until 

 it leads to a more fortunate issue. The iin ai'iahh' 

 "pull" or "push" of the tropism theory is not regartled 

 as the primary phenomenon, though an observer who 

 viewed only the end results of the process might easily 

 believe that they had been brought about by such a di- 

 recting influence. 



Here, again, it is not my purpose to discuss the merits 

 of these rival hypotheses. It is possible, indeed, that 

 they should be regarded as complementary, rather than 

 antagonistic. Jennings admits that n-sijoiiscs which 

 originally were performed according to the nicthod of 

 "trial and error" may, through thr al)hrt'\iatiiig infhi- 

 ence of habit, come to be determined more (lirectl>- by 

 the stimulus. But, however we may view the method of 

 origin of these responses to stinmli. it seems ph-iin tliat 

 any adai)tiveiiess that we meet with is eontingenl in the 

 sense in whieh I have already used tlie term. Aerording 

 to tlie investigations of .lennings, tlie or-anism reaehes 

 an optinnim environment by chance, and remains there 

 because it is stimulated to change its course whenexcr it 

 begins to pass out of this environment. 'IMiat unfaxor- 

 able stimuli should provoke these changes of hchax ior 

 need not be attributed to any "primaiy pur])osefnhiess*" 

 in living matter, since w(> can l»e ])erfeetly sure that any 

 organisms ])eha\ ing ditferently wouhl be sjieedily elimi- 

 nated. 



Again, I take it that the ehief a.lvoeat." of the theoiy 

 of direct orientation would l)e the la>t to assume a ])vh\- 

 ciple of primary adaptedness. and w(ud(l admit that any 

 utility connected with these ••tropisnis" must have been, 

 in the first instance, a i)ure eoineidenee. In tiu' case of 

 an organism, "•irri'sistil)l\ " drawn toward a favorable 



