316 A. A. SCHAEFFER. 



(A grain of globulin which was next presented was, after some 

 uncertainty in behavior, finally ingested in a food cup pointing 

 upwards.) A few minutes after the globulin was ingested another 

 grain of tyrosin was laid in the ameba's path 18. The ameba 

 moved into contact with it and then ingested it while moving on 

 over it. No period of rest ensued. Another grain of tyrosin 

 was then laid a little to the right of the ameba's path, but before 

 coming quite into contact with it, the ameba moved away to 

 the left. 



This series of experiments shows very well the effect of previous 

 behavior upon a closely following reaction. First, two trials 

 with tyrosin produced negative behavior. The third trial re- 

 sulted in indifferent behavior, doubtless because it was the third 

 time the test substance had been encountered. The ameba was 

 a long time in eating a grain of globulin which was next presented, 

 and at first the ameba reacted indifferently toward it. It is 

 more than likely that the previous experience with tyrosin 

 developed this condition of indifference in the ameba. But this 

 condition was entirely overcome by the reactions involved in 

 eating the globulin, for when the next grain of tyrosin was pre- 

 sented, it was ingested. Thus the effect of previous behavior 

 influenced the ameba's succeeding reactions more than the nature 

 of the stimuli received in these reactions. But the newly created 

 tendency to positive behavior was of short duration, for when 

 another grain of tyrosin was presented only mild positive be- 

 havior, followed by avoidance, was observed. 



A tyrosin grain was placed in the path of another granular 

 ameba 51. Very remarkable behavior followed. The ameba 

 moved forward into contact with it and then proceeded to flow 

 on over it. When the anterior end lay over the tyrosin, it formed 

 itself into an inverted shallow cup over the tyrosin 55. But 

 no sooner was the food cup formed and ready to close up over 

 the tyrosin than the anterior end was lifted up, away from the 

 tyrosin, and the middle and posterior regions of the ameba con- 

 tracted. The effect was of course to remove the anterior end 

 of the ameba from the dissolved or dissolving tyrosin. The food 

 cup was completed however and persisted in the ameba for some 

 time. The ameba moved away from the tyrosin for a short 



