56 ASA A. SCHAEFFER. 



for the effect of the light was continually decreasing in intensity 

 as the ameba moved away from it. The light would therefore 

 be expected to have the maximum effect at maximum intensity, 

 which was when the tip of the ameba was closest to the light. 

 It is improbable therefore that the throwing out of a pseudopod 

 and the bending of the tip to the right were caused by the imping- 

 ing of the light rays at that region at that time. It is possible 

 that this behavior is the result of the cumulative effect of the 

 light rays while the ameba was passing the beam. There was 

 formed a tendency toward a positive reaction some few seconds 

 before it expressed itself in visible change of behavior, and when 

 this tendency "came to a head" it resulted in exaggerated be- 

 havior; for two pseudopods were thrown out on the stimulated 

 side and at the same time the tip of the ameba was turned to the 

 right. This feature of ameban behavior the formation of two 

 pseudopods on the stimulated side, one near the anterior end 

 and the other opposite the stimulating object after the tip of the 

 ameba has passed the stimulating object is frequently observed 

 and is of great interest. It indicates several things. First, it 

 effectively disposes of the hypothesis that the movement of 

 pseudopods toward an object is directly induced by the object. 

 Second, it shows that there is some sort of a coordinating or 

 integrating agency at work in the ameba so that the larger part 

 of it, at least, tends to react in a coordinated manner, even if there 

 are separate centers of reaction. When the posterior pseudopod 

 came into contact with the light, negative behavior set in sud- 

 denly. The pseudopods on the right were promptly withdrawn 

 and two others were rapidly projected on the left. Nevertheless; 

 the ameba finally moved on in the original direction. 



Violet Light. The violet light that was selected was as near to 

 the end of the visible spectrum as possible, A beam of violet 

 light was projected on the right of a proteus 230. A small 

 pseudopod was thrown out on either side 232 the one on the 

 right being directed toward the light. The ameba moved away 

 however through the pseudopod on the left. The ameba was 

 shifted with the light again on the right 235. The tip of the 

 main pseudopod turned to the right and moved into contact with 

 and then on over the light. The ameba was shifted with the 



