238 'Journal of Comparative Neurology and Psychology. 



6. The larvae were placed in the glass-bottomed box over the 

 light-shaft; fifteen minutes was allowed for the first orientation, and 

 five minutes was given for each of the others: 



After 



Blue. 



Green. 



Orange. 



Red. 



15 minutes. 

 .20 minutes. 

 25 minutes. 

 30 minutes. 

 35 minutes. 

 40 minutes. 



Totals 



6 2 



6 I 



4 I 



4 S 



3 7 



2 7 



^5 



23 



It thus appears that the photopathic reaction of the larVcie was 

 definitely positive. After this series of observations the larvae 

 were returned to the glass jar and placed on the west table. In the 

 faint daylight which remained, the positive reaction was manifested 

 and continued as long as the light lasted. 



Conclusions from Experiments 20, 21, 22 and 23: As has been 

 noted, these experiments deal with the reaction of larvae as they 

 pass through the third and enter the fourth stage. In Experiment 

 20 (Cases 2, 3, 4 and 5) it was shown that, in general, the majority 

 of early third-stage larvae reacted negatively, frequently to light 

 of weak intensity, and invariably to light of greater intensity. In 

 Experiment 21 it appears (i) that this negative response was fairly 

 characteristic of the early third-stage larvae; (2) that, notwithstand- 

 ing this negative phototactic reaction, the photopathic response 

 might be definitely positive (Experiment 21, Case 3) thus appear- 

 ing to indicate that, at least at a certain period in the life of the 

 third-stage larvae, a positive photopathic reaction and a negative 

 phototactic response may be given by the same individual. Experi- 

 ment 22 demonstrates (i) that, as the third-stage advanced, the 

 positive reaction, was more frequently and more easily determined 

 by light of all intensities (Case 2), and that an increasingly strong 

 illumination was required to bring about a negative reaction (Case 

 4); (2) that the photopathic response, if anything, remains through- 

 out the stage, positive (Case 3), while the sign of the phototactic 

 response may change with the intensity of the light (Cases 2 

 and 4). 



In Experiment 23 it is observed that the negative reaction to 

 strong light was still prominent in the behavior of the twelfth-day 



