162 



WILLIAM L. DOLLEY, JR. 



These results show that the stimulating efficiency of inter- 

 mittent light depends not only on the flash-frequency but also 

 on the ratio between the duration of the flashes and the intervals 

 between the flashes. This conclusion is evident if the lights 



FIG. 3. Paths of a typical specimen of Vanessa in a field of light composed of 

 two horizontal beams of equal illumination, 7 m.c. crossing at right angles, the 

 light in one beam being continuous and that in the other intermittent. (Reduced 

 by three-fourths). The intermittent light was produced by a disk with one-half 

 removed. Other explanations of this figure are the same as those already given 

 in the description of figure 2. Note here also that the degree of deflection varied 

 with the flash-frequency. 



