128 Studies in Animal Behavior 



gry condition. Hydra when not fed for some time 

 extends the body, sways about in various directions 

 and keeps up a restless movement of its tentacles, 

 thereby increasing its chances of contact with the 

 small creatures which serve as its prey. 



Instances of the non-intelligent modifications of 

 behavior might be multiplied indefinitely. As we 

 pass to higher forms the capacity for responding in 

 different ways to a given situation becomes greatly 

 increased. "Nature," says James in his admirable 

 chapter on instinct, "implants contrary impulses to 

 act in many classes of things, and leaves it to slight 

 alterations of the conditions of the individual case 

 to decide which impulse shall carry the day," and 

 he points out that many animals lose the instinctive 

 demeanor and appear to lead a life of hesitation 

 and choice, not because they have no instincts, but 

 because they have so many of them that they block 

 one another's path. Intelligence in the accepta- 

 tion of the term which we have adopted begins with 

 the formation of associations. It does not make its 

 appearance, so far as is known, until a compara- 

 tively high stage of organization has been attained. 

 The evolution along the lines of complexity of in- 

 stinct and ready modifiability of reactions to suit 

 new conditions, affords a substantial basis for in- 

 telligent behavior. Without such evolution the 

 power of associative memory would avail little. 

 But with a large number of readily modifiable in- 

 stincts, associative memory becomes the means of 



