418 WILLIAM L. DOLLEY, JR. 



certain angle with the rays, the response varies. Usually, how- 

 ever, if the luminous intensity is suddenly increased the butter- 

 flies increase the angle of deflection, and if the intensity is sud- 

 denly decreased, they decrease the angle of deflection. These 

 results are probably dependent upon the time-rate of change and 

 are not due to the difference in the amount of light energy received 

 by the functional eye under the different conditions. 



10. Vanessa antiopawith one eye blackened can re-orient. If, 

 when the animal is moving toward a source of light, the direction 

 of the rays is changed so that the light strikes the butterfly on 

 the side of the blinded eye, the organism changes its direction of 

 motion by turning directly toward the source of light. If the 

 source of light is moved to the other side of the animal, the 

 butterfly again changes its direction of motion and goes toward 

 the light. Thus, with one eye functional, the animals in orient- 

 ing may turn either toward the side bearing the functional eye, 

 or toward the side bearing the blinded eye. These results con- 

 tradict the assumption of the 'continuous action theory,' that 

 orientation is dependent upon the relative amount of light energy 

 received by the two retinas. 



11. Specimens of Vanessa with one eye blackened move in 

 circles toward the blinded eye when placed in darkness, while in 

 light they tend to turn in the opposite direction. This shows 

 that the covering of the blackened eye produces a stimulus. It 

 also shows that the circus movements toward the functional eye 

 in the presence of light are due to a stimulus produced by light, 

 and are not due to stimuli received bj^ the blinded eye. 



12. When suspended above a rotating disc with the head 

 pointing toward the center of the disc, and with only one eye 

 illuminated, Vanessa attempts to turn toward the illuminated 

 eye. Under such conditions there are alternate periods of rest 

 and activity. The stimulus initiating a period of activity is not 

 due to change in luminous intensity, and hence it must be due 

 either to internal factors or to the continuous action of light. 



13. If, however, the light is so arranged that only the anterior 

 surface of the right eye is illuminated, the animal may turn 

 either to the right or to the left. This indicates that the reac- 



