188 THE PROBLEMS OF EVOLUTION 



irregularity of instinctive action. Individuals vary 

 within a species, and the individual itself may 

 sometimes do one thing and sometimes another 

 under similar conditions. Finally he records among 

 these highly instinctive little animals cases which 

 can be understood only by granting that insects 

 have the rudiments of intelligence. When acci- 

 dental occurrences, depending upon peculiar and 

 seldom-repeated circumstances, are met by actions 

 which are distinctly suited to the unusual condi- 

 tions, we cannot fall back on unmodified instinct 

 as an explanation. 



From a slight degree of adjustment of behavior 

 to conditions, to the complex intelligence of man 

 is only a matter of increasing complexity. The 

 difference is great, to be sure, but the transition 

 is not difiicult to grasp. 



What of the importance of these things in evolu- 

 tion.^ Does the behavior of an animal lead to 

 change.'^ Is it, in itself, a force which may lead to 

 new development in the organism.^ Or is it simply 

 and solely a coordinating factor? And if it is merely 

 coordinative, has it any important relation to the 

 question of evolutionary change .^^ 



If we refer to the simplest manifestation men- 

 tioned, the tropism of the simple animals, we note 

 that the result of a stimulus is always the most 

 effective orientation possible for the maintenance 

 of the animal in its normal state. Change is not 



