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THE AMERICAN NATURALIST [Vol. LIII 



have already solved. This is the more true the more 

 complex our problem. The "newness" of the latter may 

 relate to a very few features, the residue consisting of 

 elements which, in the last analysis, have been solved in 

 an entirely empirical fashion. And the same may doubt- 

 less be said of those adaptive physiological responses 

 which are generally assumed to be unconscious. As re- 

 gards the fixed reactions lmo^vn as "tropisms," I have 

 already pointed out the probability that the predomi- 

 nantly adaptive character of these has been the outcome 

 of racial history and therefore of some form of selection. 



V. Evolution and Contingency" 

 In the two preceding sections of this paper stress has 

 been laid upon manifestations of the power of self- 

 adaptation in the individual organism. Very little has 

 been said regarding those fixed structural and functional 

 mechanisms by which the more usual needs of life are 

 provided for. The origin of such structures and func- 

 tions— ''adaptations," as they are familiarly called— 

 must bo accounted for in any adequate theory of evolu- 

 tion. Xow. f liiive already argued that no theory of evo- 

 liitiDii. so r.ii- as it is scientific, can admit the possibility 

 that tlir iircds of tlio organism may call forth in any 

 direct way the initiation of those processes by which 

 these needs com.- to lie satisfied. Let us look somewhat 

 further into this (nicstioii. 



The field of organic evolution is one which has lent 

 itself in a high degree to vitalistic and quasi-vitalistic 

 exploitation. From the time of the establishment of the 

 doctrine of descent, there were always persons who, in 

 spirit, still clung to the creation principle, while accept- 

 ing in form the newer ideas. Indeed, among biologists 

 themselves, there have always been those who have seen 

 in organic evolution the working out of a "perfecting 

 principle," in a large degree independent of environ- 

 ment. Even Lamarck, who propounded one of the chief 

 naturalistic accounts of this process, admitted that life 



