REACTIONS OF AMEBA TO LIGHT. 55 



astheamebamovedon. When shifted again with the blue light 

 to the left 20 1 the ameba turned toward the light and then 

 passed on to the left. The ameba again reacted positively when 

 shifted with the light straight ahead 204. When shifted again 

 the ameba reacted positively but rather uncertainly 209. In 

 the next experiment, with the beam of blue light on the left, 

 negative behavior was induced 216. 



A beam of pure (see footnote p. n) blue spectral light was 

 projected to the right of a dubia 219. The ameba moved past 

 the light spot for a considerable distance without any change in 

 behavior. Then two pseudopods were sent out: one directly 

 toward the light, and the other near the tip, but also on the right 

 side 220. As the pseudopods enlarged, the tip of the ameba 

 also turned sharply to the right 221. When the posterior 

 pseudopod came into contact with the light, the pseudopods on 

 the right were retracted, and two others thrown out on the left 

 222 but these also were retracted after a few seconds, and 

 the ameba then moved on in the original direction. The ameba 

 was then shifted with the blue light lying directly ahead 223. 

 The tip of the ameba (only the tip of the ameba is shown) 

 turned to the left 224 but a pseudopod was thrown out on the 

 right toward and into contact with the light 225. The ameba 

 flowed partly over the light 226 but withdrew from it later 

 and moved off through a pseudopod on the right. 



Summary. There is no marked difference between the 

 reactions toward red light and those toward blue. Blue light 

 induces positive behavior in as marked a degree as red, though 

 when all the experiments are considered, red light seems to be 

 somewhat more attractive than blue. Blue light, like red and 

 white, induces both negative and positive reactions. Blue light 

 can also be sensed at a distance. 



The experiments with the dubia 219-222 are interesting 

 inasmuch as a pseudopod was thrown out at the tip of the ameba 

 on the side on which the light lay, some time after this part of the 

 ameba had passed the light. It may be noted also that the tip 

 of the ameba turned strongly in the same direction. It appears 

 quite unlikely that the light acted as an efficient cause on this 

 region of the ameba at the time of the formation of the pseudopod, 



