224 'Journal of Comparative Neurology and Psychology. 



toward the window; the position of the red and orange glass was 

 also reversed. The distribution at the end of each test was as 

 follows : 



Case 2 — Next, green and blue glass plates w^ere substituted for 

 the red and orange, the method of the experiment otherwise remain- 

 ing the same, and the green and the blue glasses were reversed in 

 position at the end of each test. A series of four tests showed the 

 following results : Green arm, 1 1 ; stem, 2 ; blue arm, 27. 



i 



1 i 



A B 



Fig. 5. Showing the Y-tubes as set up for experiment. The arrows indicate the direction of the 

 light rays. The cross-hatched areas represent the glass plates of the darker color laid over the arms 

 of the tubes. The ends designated a, represent the starting point for the negatively reacting (A), or 

 the positively reacting (B), larvae. 



Case J — One more test of the reaction of this group of positive 

 larvae was made at this time, which was far more delicate than 

 either of the preceding, for the difference in the intensity of the 

 glass plates used was less. In making a selection of glass slides 

 two were chosen which had been purchased for "red glass." On 

 close inspection, however, and by test with sensitized paper, it 

 was observed that one slide was somewhat lighter in color tone than 



