REACTIONS OF LAND ISOPODS TO LIGHT 



209 



TABLE 3 



Reaction of Oniscus A 12 to directive light of 12.955 CM., showing results of daily 

 tests for 15 days. Tests were made with the animal facing the light (A), facing 

 away from the light (B), and illuminated on the right (C) and left (D) sides 



1 A second set of responses was recorded on the eleventh day. 



to the eight degrees of negativeness just referred to and the nu- 

 merals on the ordinates being the number of responses which 

 fall into each of these eight classes. The lines A, B, C, D repre- 

 sent the four positions with respect to the light in which the 

 animal was placed, while the dotted line is the average of the four 

 positions. 



As would be expected, the greatest degree of negativeness is 

 when the animal is headed away from the light, and the lowest, 

 when facing the light. As only data in classes 1 and 2 on the 

 abscissa indicate a positive response, all of the curves show that 

 this isopod was thoroughly negative. There is a close corre- 

 spondence between the nearly identical reactions in positions C 

 and D and the average for all positions. This indicates that the 



