338 A. C. WALTON 



These averages are based on the results of 500 trials at each 

 of the eleven intensities of light and contain the individual 

 records that do not harmonize with the final conclusion, namely, 

 that a higher intensity of light is accompanied with a higher 

 rate of locomotion. In a series of 200 trials, animals were 

 started under the highest intensity of light and carried through 

 each intensity to the opposite extreme and back to the starting 

 point. In a second test a similar course was run except that 

 it started and ended with the lowest intensity of light. The 

 results of these two series are shown in the form of curves of 

 response in Fig. 1, in which the intensities are plotted as ab- 

 scissae and the distances in centimeters per minute as ordinates. 



The heavy line represents the curve of response for the animals 

 that began at the lowest intensities and the broken line that for 

 animals which began at the highest intensities. These two 

 curves practically coincide, thus showing, among other things, 

 that the mechanical stimulation of placing the animal in the 

 hanging drop did not cause an abnormal movement at the 

 beginning of a series of trials. 



Trials were also made in which the stimulus was changed 

 suddenly from one extreme to the other. The response of the 

 animals in such cases was different from that which the pre- 



