BRADLEY M. PATTEN 



449 



5 and 6 shows that the reactions under lateral and under anterior 

 illumination are qualitatively the same. 



Quantitative comparison based on the percentage reduction of 

 the normal reaction in each case shows a correspondence which is 



a. 



Fig. 6. Reactions to anterior illumination in animals which had been subjected 

 to symmetrical interference with their photoreceptive mechanism. The circle 

 represents the observation circle of the apparatus; the group of arrows, the direc- 

 tion of the light beam; the silhouette of the scorpion, the animal's position when 

 subjected to anterior illumination; the dotted arrow, the average reaction of nor- 

 mal animals; the soHd arrow, the average reaction of the experimental animals. 

 a. Animals with both median eyes capped, b. Animals with both lateral eyes 

 capped, c. Cutaneous sensitive areas on both sides blackened, d. Both median 

 and both lateral eyes capped, e. Both cutaneous sensitive areas and both lateral 

 eyes blackened. 



within the limits of experimental error, when the differences in effec- 

 tive illumination due to the anatomical position of the receptors is 

 taken into consideration (see below). 



