446 



PHOTOREACTIONS OF WHIP-TAIL SCORPIONS 



was based on the degree of orientation attained while the animal was 

 traveling over a standard distance, thus takmg into account the tune 

 factor. 



Fig. 4. Graphical summar}' of reactions to balanced illumination in animals 

 which had been subjected to symmetrical interference with their photoreceptive 

 mechanism. The circle represents the observation circle of the apparatus; the 

 groups of arrows, the direction of the light beams; the silhouette of the scorpion, 

 the animal's position when subjected to bilateral illumination; the shaded seg- 

 ment, the average path of normal animals; the curved radial arrows, the average 

 paths of experimental animals (based on ten trials), a. Animals with both median 

 eyes capped, b. Both lateral eye groups capped, c. Cutaneous sensitive areas 

 on both sides blackened, d. Both lateral and both median eyes capped, e. 

 Both lateral eyes and the cutaneous sensitive areas on both sides blackened. 



The reaction measurements made on symmetrically blinded ani- 

 mals subjected to lateral illumination are collected in Table V and in 

 Fig. 5. The solid arrows represent the average path followed by the 

 partially blinded animals, the dotted arrows the average reaction of 

 normal animals under the same conditions of illumination. 



