78 Studies in Animal Behavior 



Now there are undoubtedly forms to which Loeb's 

 remarks are entirely applicable. The possibility of 

 the interpretation which Loeb has given was care- 

 fully considered by the present writer while work- 

 ing on the forms above described and was finally 

 rejected as inadequate for the particular cases un- 

 der consideration. It was pointed out that "a trop- 

 Ism of the direct sort is not necessarily a perfectly 

 fixed and rigid affair. It may be a tendency more 

 or less obscured by a lot of random movements 

 arising from internal causes. An organism may be 

 drawn to a certain point through a direct orient- 

 ing reflex, but if there Is at the same time a large 

 element of random activity in its behavior it may 

 seem to reach that point by the method of trial 

 and error." 



A careful consideration of the movements of 

 earthworms, leeches and fly larvae made it evident 

 that orientation does not take place by the method 

 just referred to. We are not dealing merely with 

 the masking of a simple troplsm by a lot of inconse- 

 quential activity. It Is largely by virtue of and not 

 in spite of random movements that orientation Is 

 secured. If an organism were so constituted that 

 whenever it extended toward the light it would 

 jerk back and turn to one side, even though the di- 

 rection of Its turning were totally indeterminate, it 

 would finally become oriented away from the light. 

 To a considerable extent the reactions of the forms 



