

i 



Modification by Experience 249 



arms. The very versatility of the starfish, this writer 

 thinks, tells against its perfecting any one movement, 

 through experience (260). Stentor and Hydra go through (I 

 the same series of reactions each time, without apparently J 

 being influenced by their previous behavior. And again A 

 we must remind ourselves that there is no reason why their/ 

 conduct, adaptively regarded, should be otherwise. Aa^ 

 animal with so httle power of distinguishing qualitative^ 

 differences among stimuh cannot be in any way awarea 

 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 moftientarily interrupted; while contraction on 

 the stem and breaking loose from its moorings are st 

 more serious infractions of the normal routine. It woul 

 be decidedly disadvantageous to take the last step whil 

 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 onlyn 

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

 one case where, in a supreme emergency, the stimulusJ 

 being not only repeated but increased in intensity, everW 

 possible outlet- is tried, whether it has any fitness to th^ 

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

 effect of increased temperature on the reactions of pla- 



