FITNESS 5 



by an almost infinite series of adaptations of 

 life to its environment, whereby, through a 

 corresponding series of transformations, pres- 

 ent complexity has grown out of former sim- 

 plicity. 1 



The great and fruitful ideas which Darwin 

 brought to the attention of the whole world 

 have long since been incorporated into hu- 

 man thought. Not the least important 

 among them is the new scientific concept of 

 fitness, as it emerges from the discussion of 

 natural selection. Before Darwin, this concept 

 possessed all the vagueness of an idea which, 

 though in part founded on observation, was 

 not to be explained with the help of existing 

 scientific theories. But although Darwin's 

 fitness involves that which fits and that which 

 is fitted, or more correctly a reciprocal rela- 

 tionship, it has been the habit of biologists 

 since Darwin to consider only the adaptations 

 of the living organism to the environment? 



1 The ideas which are associated with the names of de 

 Vries, as well as the very different hypotheses of Driesch, 

 Bergson, and others are, of course, concerned with the manner, 

 not with the fact of adaptation and organic evolution. 



2 Far different was the earlier point of view. An examina- 

 tion of Whewell's Bridgewater Treatise at once reveals im- 

 portant, if often fallacious, discussions of environmental fit- 

 ness ; e.g. " It has been shown in the preceding chapters that 

 a great number of quantities and laws appear to have been 

 selected in the construction of the universe ; and that by the 



