302 BEHAVIOR OF THE LOWER ORGANISMS 



ward, so as to try successively many different directions. The behavior 

 shows the "method of trial" reduced to a system. It would be almost 

 impossible to suggest any modification of this reaction, as exemplified 

 in Paramecium, that would make it better fitted, under the given rela- 

 tions, for meeting all sorts of conditions. In fixed infusoria, such as 

 Stentor, this behavior is modified to adapt it to the fixed life. In the 

 free-swimming animal the organism is subjected to new conditions every 

 time the reaction is repeated, hence there is little occasion to try other 

 methods of behavior. But if the organism is fixed in one place, this is 

 not true ; when a given reaction is repeated it merely brings on the same 

 conditions its first performance induced. So different methods are de- 

 veloped. Under unfavorable conditions the organism first turns to one 

 side, then reverses its ciliary current, then contracts, etc. (see p. 174), 

 trying many different changes of behavior. In Hydra, in the starfish, 

 in the flatworm, we have seen this same "method of trial" appearing 

 under various forms. In all these organisms persistent unfavorable 

 stimulation induces first one physiological state, then another, then 

 another, and to each state there corresponds a certain method of 

 behavior. 



C. Selection from the Conditions produced by Varied Movements 



In all this behavior we find the manifestations of a most important 

 principle, one of far-reaching significance for the understanding of be- 

 havior. The stimulus does not produce directly a single simple move- 

 ment (a reflex act), of a character that relieves the organism at once 

 from the stimulating condition. On the contrary, stimulation is followed 

 by many and varied movements, from which the successful motion is 

 selected by the fact that it is successful in causing cessation of stimula- 

 tion. This is the principle of the "selection of overproduced move- 

 ments," of which much use has justly been made by Spencer, Bain, and 

 especially by Baldwin (1897, 1902), in attempting to explain behavior. 

 It is more accurate to speak of the selection of the proper conditions of the 

 environment through varied movements. It is primarily the proper en- 

 vironmental conditions that are selected; the movements are only a 

 means to that end. From this point of view what we have often called 

 in the foregoing pages the method of trial may be formulated as follows : 

 When stimulated the organism performs movements which subject it to 

 varied conditions. When in this way it reaches a condition that relieves 

 it of stimulation the reacton movement ceases, since there is no further 

 cause for it. The organism may then resume its usual movements. In 

 the case where the reaction consists of changes in direction, as in infuso- 



