Holmes, Random Movements. 107 



important role played by the method of trial and error in the 

 behavior of the lower organisms, especially the protozoa In the 

 work that has been done on the instincts and reactions of ani- 

 mals in recent years too much stress has doubtless been laid 

 upon the action of the environment on the organism and too 

 little upon the internally initiated actions of the organism itself. 

 Animals are frequently regarded as if they were more or less 

 passive instruments played upon by external agencies and re- 

 sponding in the right way because they are so constructed that 

 they cannot do otherwise. Rather, they are like instruments 

 running by their own inherent energy, like a music box that is 

 wound up and so regulated as to produce a variety of melodies. 

 External agencies press the stops here and there and change 

 the tune. If one tune does not suit, the environment is heard 

 from and the instrument shifts to another. 



The method of trial and error in its widest sense is one of 

 those very large categories under which a multitude of varied 

 activities may be subsumed. Even the process of natural se- 

 lection may be considered a form of it, since all variations may 

 be regarded as trials, and the unsuccessful ones errors. By a 

 little squeezing we might also include many of the phenomena 

 of development and regeneration. In psychology it is comnion- 

 ly recognized not only as the method of primitive animal intelli- 

 gence, but as forming an essential element of the process of rea- 

 soning in its more abstract forms. Now it is coming to be read 

 back into the realm of instinct and tropisms. In all these fields 

 it is, par excellence, the method of adaptation. Instinctive be- 

 havior is either a direct expression of it, or, so far as instincts 

 are stereotyped, indirectly the outcome of it through the prin- 

 ciple of natural selection. 



The role played by the trial and error method in the be- 

 havior of the lower organisms has, as yet, elicited but little com- 

 'ment, owing probably to the fact that attention has been cen- 

 tered more upon other features of their behavior. It may have 

 been considered by some investigators as too obvious for re- 

 mark since anyone who attentively observes the conduct of 

 almost any of the lower animals for ten minutes can scarcely 



