2 20 LIGHT AND THE BEHAVIOR OF ORGANISMS 



were collected and brought to the laboratory. These speci- 

 mens were exposed one at a time in light from a single 

 source; they all oriented directly and fairly accurately. If 

 placed on the table in the beam of light so that one side 

 faced the glower they turned slowly but directly until they 

 faced the light and then hopped or walked toward its source, 

 stopping frequently for a few moments at intervals on the 

 way. The light from both glowers was now turned on and 

 the specimens were exposed, one at a time, in the beam 

 having the lower intensity, in such a position that after 

 they oriented and moved toward the source of light they 

 soon reached the more intense lateral light from the second 

 glower, which of course illuminated one side. I was some- 

 what surprised to find that ordinarily there was no apparent 

 reaction whatever when the specimens reached the beam 

 of lateral light, although the intensity of this was twice as 

 high as that in which they were oriented. The toads con- 

 tinued on their way just as though there' had been no 

 lateral illumination. All the other organisms studied in 

 light from two sources proceeded toward or from a point 

 between the sources of light. The toads always went 

 directly toward one or the other of the two sources. 



Each of the seven specimens under observation was 

 studied while it crossed the field six times, and all but one 

 continued toward the glower which produced the beam in 

 which they were first oriented, without any perceptible 

 deviation on account of the lateral light from the second 

 glower. Only one specimen turned when it reached the 

 lateral illumination. It did not however go toward a point 

 between the two glowers as might have been expected, judg- 

 ing from results of previous experiments on other forms. 

 It proceeded directly toward the glower which produced 

 the lateral illumination. In no instance was there any evi- 

 dence of movement toward a point between the two 

 sources. 



These results do not support Loeb's recent statement 

 regarding orientation in light from two sources. He says 



