QUANTITATIVE DETERMINATION OF LIGHT REACTIONS 245 



PERCENTAGE DIFFERENCE IN LIGHTS 



Fig. 15 A curve representing the angular deflection under opposed lights of 

 graded differences of intensity, based on the measurement of 2600 trails ; see also 

 table 5. 



larva's scale of reactiveness to differential bilateral stimulation 

 by light. Such a curve has been constructed in figure 15, plotting 

 angular deflection along the axis of ordiriates and percentage 

 differences along the axis of abscissas. Figure 16 shows nine 

 pairs of trails made at the nine intensity differences used to plot 

 the curve of figure 15. These particular trails were selected 

 because they coincided with the average deflection of all the 

 trails run at the stated differences of intensity and therefore 

 give a very clear picture of the experimental results on which the 

 curve was based. 



