228 'Journal of Comparative Neurology and Psychology. 



Case 5 — July 23, I p.m. Twenty fifth-day, second-stage larvae 

 were taken from one of the hatching bags and put in the glass jar. 

 This was placed in the dark box and the larvae were submitted to 

 illumination from the red light. There was some random swim- 

 ming, but the general reaction was positive, except in white light, 

 in w^hich three were positive and seventeen negative. Next, the 

 jar was removed from the dark box and placed on the west table 

 in subdued sunlight. Here the reaction was definitely negative. 

 At 4:30 when the jar was returned to the box (at this time in the 

 afternoon the light was much less intense than earlier) a positive 

 reaction was obtained in red, orange and green light. 



Conclusions from Experiments 16, 17, 18: From the result of 

 the last three experiments the following tentative conclusions may 

 be drawn. The general negative reaction to light of great inten- 

 sity, begins on about the third day of the first stage, continues for 

 the most part uninterruptedly until the moulting-period is near; 

 just before the moult the. reaction becomes indefinite or, more 

 often, positive; directly after the moult into the second stage 

 (which occurs on the fourth or fifth day of the first-stage-period), 

 the reaction to lights of nearly all intensities again becomes defi- 

 nitely negative. 



2. Second Larval Stage. 



Expcrnnent ig. Case I — July 19, 8:30 a.m. Observation of a 

 group of sixth-day, recently moulted second-stage larvae demon- 

 strated that a negative reaction took place when the larvae were 

 put in the glass jar and placed in the dark box. This was true for 

 daylight coming through the three by three inch window, and in 

 both blue and green light. In the case of orange and yellow light, 

 however, the reaction was similar to that in either yellow or orange, 

 but perhaps less definite. It may be here recorded that a group 

 of first-stage larvae, about one and a half days old, subjected at 

 the same time to these conditions, gave a positive reaction, not only 

 in orange, but also in blue, and even to white light. These reac- 

 tions took place on both black and white backgrounds, but they 

 were more definite on white. But when the stimulus of the orange 

 rays was continued for ten minutes or more, in this case also, the 

 negative reaction began to appear again and many larvae came to 

 the room side of the jar. 



