REACTIONS OF LAND ISOPODS TO LIGHT 



207' 



TABLE 1 



Reaction of Oniscus A 10 to directive light of 12.955 CM., showing results of daily 

 tests for 17 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 When less than 20 responses are recorded, the animal failed to respond in 

 the other instances. 



tive section of the field is only 25 per cent of the whole. How-" 

 ever, the 5,9 per cent calculated shows that the animal was 

 unquestionably negative. The occasion when it would naturally 

 have gone toward the light if it were indifferent, was when it was 

 facing the light at the start, but even under that condition it 

 turned away in 91.7 per cent of the trials. 



A similar tabulation of percentages is shown in table 2 for 

 Oniscus A 11, tested for fifteen days. 



A higher record of positiveness was made by Oniscus A 12, 

 which received fifteen daily tests. Most of the positive responses 

 came in the first four days, the animal being 45 per cent positive 

 on the first day. After the fourth day, the reaction was as 



