REACTIONS OF WHIP-TAIL SCORPION TO LIGHT 



265 



TABLE 6 

 Reactions to Masligoproctus with the lateral eye group on one side of the head cov- 

 ered. Animals were subjected to bilateral stimulation by equal opposed lights, 

 each of 120 candle meters intensity. Compare these reactions tvith normal reac- 

 tions (table Jj) to the same conditions of illumination 



normal animals under identical experimental conditions (table 4) 

 can leave no doubt as to the effectiveness of asymmetrical inter- 

 ference with the photoreceptors, in producing a correspondingly 

 unbalanced reaction. 



Before leaving the work with normal animals, it seemed advis- 

 able to test their reactions to a considerable range of intensities. 

 Aside from the interest attaching to a determination of the 

 threshold of sensitivity to light, there are special considerations 

 in connection with the problems in hand which make desirable 

 the securing of such data. In any opaque animal, owing to the 

 shadow of the body, the illumination actually effective on the 

 photoreceptors varies greatly from the photometrically determined 

 illumination. Furthermore, in experiments which involve the 

 elimination of part of the receptive mechanism, the total effec- 

 tive illumination would be greatly reduced as compared with 

 that received by normal animals under the same experimental 

 conditions. If we should happen to be dealing with an animal 



