CONTINUOUS STIMULATIONS VERSUS TRANSITIONAL SHOCK 67 



were free to move and naturally changed in position somewhat 

 as the insect became active. By observing the shadow of the 

 head when the insect was moving its legs it could be seen that 

 the head did in fact move up and down. Whenever the insects 

 were active, however, "they attempted to turn toward the func- 

 tional eye, never in the opposite direction/' . The results of 

 the experiments, so far as the nature of the orienting stimulus is 

 concerned, are regarded as not conclusive, "for the moment 

 the animals become active, and before they attempt to turn, 

 there is a change in the position of the eye owing to the vertical 

 movements of the head, and this, no doubt, results in changes 

 in the luminous intensity on the various ommatidia. Thus, it 

 is evident that the attempt on the part of the animal to turn 

 toward the illuminated eye may be due to stimuli dependent 

 upon the time-rate of change of intensity." So far as the but- 

 terflies responded to light at all, their behavior, while rather 

 spasmodic, was in essential agreement with what was described 

 by Miss McGraw and myself, only as the creatures jiggled 

 somewhat during the experiment it was held that the conclusions 

 drawn in our paper were "not justified." 



In order to test the question still further and to obtain results 

 which would permit of only one possible conclusion, an apparatus 

 was devised which would hold the eyes of the insect in a firmly 

 fixed position. If the eyes could be maintained in a perfectly 

 constant relation to the light the element of transitional shock 

 or differential sensibility would of course be eliminated. To 

 secure this end a piece of wood was fashioned into the shape of 

 an L with a long and a short arm. The wings of the butterfly 

 could be clamped on either side of the upper arm which was held 

 horizontally, while the body lay below with the head pointed 

 toward the shorter arm. Into the shorter arm a nail with a flat 

 circular head was driven a short distance from the end. The 

 butterfly was so placed that the front of its head abutted against 

 the head of the nail. By means of a quick drying glue the butter- 

 fly's head was cemented to the head of the nail, and left there until 

 the glue dried. With the wings firmly clamped above, and the 

 head firmly glued to the head of the nail, the activities of the 



