RESPONSIVE LIFE OF ORGANISMS 473 



serve whether this interval grows greater with repetition. 

 Observe whether the number of bites taken of the substitute 

 grow fewer after repeated trials. If the caterpillar has a 

 memory for the sort of experiences tried, how long can it 

 remember ? 



4. Observe the effects of bodily states on the activities 

 of the caterpillars by comparing their reactions when 

 hungry and when well fed; when cold and when warm. 



The record of this study may consist of an account (with 

 diagrams) of the experiments tried, and a brief statement of 

 the results. 



Sequences of automatic activities. We come now to the 

 consideration of a class of phenomena commonly known as 

 instincts. These are automatic activities, amplified and 

 serially arranged and extended until they cover often a large 

 part of the life of the individual. They are not essentially 

 different from the simpler automatic acts we have just been 

 considering. A caterpillar instinctively moves upward on 

 its food plant; but creeping is itself a sequence of events. 

 The participation of many sets of muscles is necessary, and 

 these must act successively and in progressive order. Each 

 movement is prepared for by the one that went before it. 

 The stimulus acts through the control centers. Not the 

 stimulus, but the state (position) of the body determines 

 which foot shall first be lifted and swung forward. 



Instincts proper are sequences of such actions the events 

 of the series being unlike in kind and unrepeated. The 

 preparation of the caterpillar for its transformations is a 

 performance of this type. When fully grown it ceases feed- 

 ing, crawls to a place of security (usually away from the 

 plant that has nourished it) , spins a silken cocoon about its 

 body and changes into a pupa. But before these things 

 can occur it must be full-fed, it must have a store of material 

 for further development, the rudiments of the adult organs 



