The Implications of Trial and Error 157 



tically caught in a sort of trap. Other Paramcecia 

 happening to enter the area are similarly caught, so 

 that an aggregation of individuals is gradually 

 formed. There is no orientation of the Paramcecia 

 to the diffusing chemical . The acid does not attract 

 the animals in any sense. The infusorians simply 

 give the motor reflex when they swim from acid 

 to water, and as a consequence of this simple re- 

 action a collection of individual results. 



Jennings has shown that Paramoecium responds 

 by the motor reflex to nearly all kinds of stimuli. 

 Practically its whole behavior is based on this trial 

 and error method. The organism does not directly 

 avoid injurious stimuli. The motor reflex may or 

 may not relieve it from the stimulating agent. But 

 it keeps on repeating the reaction until in time it 

 chances to be brought away from the injurious stim- 

 ulation. When favorable conditions occur, its be- 

 havior continues unchanged. The Paramoecium' s 

 philosophy of life is very simple. It consists in 

 merely following the Pauline injunction : "Prove 

 all things; hold fast that which is good." 



The same general scheme of reaction Jennings 

 found to be very widespread among the lower or- 

 ganisms. Although the reactions of the organisms 

 may be simple and stereotyped, this scheme of re- 

 sponse gives to the behavior of these forms a plas- 

 ticity and adaptiveness that keep them away from 

 injurious stimulations and in conditions favorable 

 for their existence. Where there Is "error," the 



