I98 COOK 



Various aspects of the kinetic theory have been presented in 

 earlier essays, of which the present chapters are a continuation. 

 Indeed, it is likely to become apparent to the reader that they 

 have been written at different times and that they often lack 

 unity and consistency. The same ground has in some cases 

 been traversed repeatedly and in different directions, but the 

 frequent restatement of the same distinctions appears to be 

 necessary in the development of so large and complicated a 

 subject. My thanks are due Mr. Walter T. Swingle for much 

 helpful interest and criticism. 



1. KINETIC EVOLUTION AND THE FITNESS PROBLEM. 



The theory that evolution is caused by natural selection and 

 the survival of the fittest is now commonly admitted to be inad- 

 equate, but our studies tend, as usual, to follow the beaten paths 

 of thought, and adjust themselves only with reluctance to new 

 interpretations. The point at which the selection theory becomes 

 obviously deficient is that it does not account for the fitness to 

 which the evolutionary progress is ascribed. This has given 

 rise to the attempt in recent years to penetrate farther into what 

 has been called " the problem of fitness," on the natural assump- 

 tion that more light could certainly be reached in the quarter 

 whence came the first suggestions of evolutionary illumination. 

 Nevertheless, those who have followed closely on the route of 

 natural selection have not yet come through into regions of clear 

 vision. 



Fitness is the primary idea of the doctrine of evolution by 

 selection. Fitness affords the cogs, as it were, by which evolu- 

 tion is supposed to be worked by the environment. Even if we 

 were to admit, for the argument, that evolutionary motion could 

 be caused by selection towards greater fitness, the evolutionary 

 factory would still lack the very important facility for providing 

 these cogs of fitness by which the environment could gain a 

 hold upon the species and roll them along. Some selective 

 evolutionists have assumed that environment could form the cogs 

 by impressing itself upon the species, and others that the species 

 could, as it were, wrinkle itself in response to external stimuli, 

 and thus give the environment a selective impingement. 



