388 



WILLIAM L. DOLLEY, JR. 



(fig. 10) increased the angle of deflection at the sudden change 

 of intensity, and then immediatelij decreased the ayigle of deflection, 

 although the insect was closer to the glower, is very significant 

 in showing that it is not the higher intensity which caused the 

 increase in the angle of deflection, but that it is the sudden change 

 from a lower to a higher intensity. Consequently, the sudden 

 increase in the angle of deflection that occurs in some cases, seems 



h "8 Ul //I A 



Fig. 10 Semi-diagrammatic reproduction of the records made by butterfly 

 10/8-c (left eye blackened) when the illumination was suddenly increased from 

 104 mc. to 1400 mc. The individual trials are numbered. The limits of the 

 beams of high intensity are designated by the capital letters; the beams of low 

 intensity by the small letters. X, position of the animal at the time the illumi- 

 nation was changed; arrows, direction of movement 6f animal. Note that the 

 insect usually turned sharply toward the functional eye immediately after the 

 illumination was increased, and later again in the opposite direction. 



to be a shock reaction and not the result of unequal amounts 

 of light energy received by the two retinas, as is demanded by 

 the 'continuous action theory' of orientation. Furthermore, 

 according to this theory the angle of deflection should be greater 

 in high than in low intensity. This was, however, not found to 

 be true, as is shown in table 2 and figure 9. By referring to this 

 table it will be seen that the angle of deflection in 2000 mc. 

 and in 200 mc. was essentially the same, whereas, according to 



