394 WILLIAM L. DOLLEY, JR. 



but would be compelled to perform circus movements continu- 

 ally, regardless of the position of the source of light. 



This experiment, however, throws no light on the nature of 

 the stimulus effective in orientation. Reorientation could con- 

 ceivably- occur in organisms with but one functional eye, whether 

 light exerts its orienting stimulus through its continuous action, 

 as demanded by the 'continuous action theory,' or through a 

 change of intensity, as demanded by the 'change of intensity 

 theory.' 



C. EFFECT OF THE COVERING OF THE EYE OWING TO CONTACT 



We have clearly demonstrated that Vanessa with but one 

 functional eye tends to turn toward this eye when it is placed 

 in a beam of light, and that this tendency decreases with experi- 

 ence. Are these responses due to the elimination of the action 

 of light on the blinded eye or to the effect of the contact of the 

 covering on this eye? This question was answered very con- 

 clusively by placing in darkness specimens with one eye covered. 

 In this experiment a wooden box (45 x 55 x 59 cm.) lined with 

 black cloth was used. In the bottom of this box were placed 

 sheets of paper covered with soot. The butterfly to be tested 

 was placed in the enclosure upon the sheets of paper, and an 

 opaque cover was drawn over the top of the apparatus. All the 

 experiments were performed in the dark room, many of them 

 late at night. The precautions taken were of such a nature that 

 the observer feels confident that no light could possibly have 

 reached the organisms. 



Under these conditions it was found that the animals made 

 circus movements, but in the reverse direction from that in 

 which they moved in the presence of light. With few exceptions, 

 the butterflies turned continuously toward the blinded eye, and in 

 most of the exceptional cases they showed a decided tendency to 

 curve somewhat in this direction. Only in a few cases did they 

 move in a straight line. In some of these the course was nearly 

 straight for eight or ten centimeters or more. 



