62 A. A. SCHAEFFER 



iind enlarged to a considerable extent, but it was arrested as 

 the inconspicuous vestige of 4 suddenly became activated (2302, 

 2303). The ameba finally moved away through this pseudopod. 

 The globuhn was left behind seven minutes after the food cup 

 was begun. 



This experiment is an illustration of that comparatively rare 

 occurrence under experimental conditions where the tendencies 

 toward positive and negative behavior, with regard to a definite 

 object, are nearly evenly balanced. We see here a change from 

 negative (2295) to positive (2298 to 2301) to negative behavior 

 again (2302 to 2304) . Of so many changes there can be no doubt. 

 But it is possible that there were more fluctuations between nega- 

 tive and positive reacting. Thus figures 2293 and 2293 may 

 also represent positive states. But even if these latter fluctua- 

 tions are left out of account, there is offered here a remarkable 

 opportunity of gaining an insight into the nature of ameban be- 

 havior which is not possible where reaction is decidedly and uni- 

 formly either negative or positive. 



In figure 2294 is seen the first indication of a negative reaction 

 toward the globuhn, viz., the interruption of concerted streaming 

 and the slight turning to the right. The formation of a number 

 of pseudopods in 2295 indicates a still stronger negative reaction 

 which reaches its maximum in 2297. The behavior was thus 

 far not unified, for the slight forward movement of pseudopods 

 1 and 6 in figure 2293 may be regarded as evidence of positive 

 behavior. With the retraction of these pseudopods and the 

 enlargement of 3, the behavior may be said to be negative, in- 

 volving the whole ameba. The formation of 7 shows a change 

 to positive behavior again and the ameba as a whole began to 

 react positively in a concerted manner, as is indicated by the 

 fact that the vestige of 6 became active again leading the ameba 

 directly toward the globuhn. No. 4 also increased in size slightly. 

 All the others, including 4, were slowly retracted when the globu- 

 lin was reached. The resumption of streaming in 7 indicates a 

 reception of disagreeable stimuli from the globulin (2302). 

 The retraction of 7 and the rapid enlargement of 4 indicates 

 more intensely disagreeable stimuli proceeding from the globuhn 



