Modification by Experience 249 



arms. The very versatility of the starfish, this writer 

 thinks, tells against its perfecting any one movement 

 through experience (260). S ten tor and Hydra go through 

 the same series of reactions each time, without apparently 

 being influenced by their previous behavior. And again 

 we must remind ourselves that there is no reason why their 

 conduct, adaptively regarded, should be otherwise. An 

 animal with so little power of distinguishing qualitative 

 differences among stimuli cannot be in any way aware 

 that the stimulus which affects it a second time is going, 

 as in the previous case, to be so persistent that the ordinary 

 negative reaction will not get rid of it. Further, each re- 

 action of the series performed by the animal is more dis- 

 turbing to its ordinary course of life than the preceding one. 

 The Stentor can bend to one side and still continue the 

 food- taking process ; if it reverses its ciliary action, feeding 

 must be momentarily interrupted; while contraction on 

 the stem and breaking loose from its moorings are still 

 more serious infractions of the normal routine. It would 

 be decidedly disadvantageous to take the last step while 

 there was any chance that milder measures might prevail. 

 In all probability, since the behavior just described has 

 no permanent effect upon the animal, it is physiologically 

 due, as Jennings suggests (375), to the overflow of the ner- 

 vous energy set free by the stimulus into first one channel 

 and then another. In most cases the movements resulting 

 are all adapted to getting rid of the stimulus, though only 

 one of them is successful in so doing ; but we have on record 

 one case where, in a supreme emergency, the stimulus 

 being not only repeated but increased in intensity, every 

 possible outlet is tried, whether it has any fitness to the 

 situation or not. This was observed by Mast, testing the 

 effect of increased temperature on the reactions of pla- 



