232 EDWIN G. BORING 



lamp; and again, when the animal became "unruly," it was 

 sometimes necessary to throw on two lights at once in order to 

 keep it from the sides of the tank. However, this latter expe- 

 dient was seldom resorted to and never continued for more than 

 a few seconds at the longest. After the individual had been 

 subjected to intense illumination from one side for about 30 

 minutes, it was left in the dark for 2 minutes, and then allowed 

 to glide freely for 5 minutes with non-directive illumination 

 from the light above, — an intensity of illumination approx- 

 imately one-fiftieth that from one of the lower lights. 



An attempt was made in many cases to supplement the 

 observations described by a continuation of the series, alter- 

 nating thirty -minute periods of right or left illumination with 

 five -minute periods of non-directive illumination ; but great dif- 

 ficulty was experienced in finding subjects which would remain 

 active for these extended periods under violent stimulation. 

 Many of the forty -four-minute series described were abandoned 

 because the animals would not remain active. With two of the 

 eight subjects reported upon here (B and E), however, longer 

 series were obtained, — B remaining active, with only occasional 

 mechanical stimulation, for five hours and twenty -two minutes. 

 In this connection, it should be added that, although all the 

 individuals were obtained from the same place, A, B, and E 

 were from a lot taken at a different time from the others. 



It was not found possible in all the experiments to keep the 

 exact lengths of periods constant. Now and then, especially in 

 the prolonged series upon individuals B and E, the animal 

 would become sluggish and it would be necessary to terminate 

 the trial before the thirty minutes had elapsed. The four minutes 

 in the dark and the five minutes in the subdued light would, 

 however, frequently refresh it enough to permit the starting 

 of a new trial. In the two prolonged series, whenever the sub- 

 jects became very sluggish, it was necessary to stimulate them 

 to activity by a slight prod with a stiff hair. In such a case, 

 a subject was prodded only after it had remained inactive for 

 two minutes. This procedure was considered allowable, as the 

 important factors— -namely, the direction of turning and the con- 

 tinued exposure of one side to light — were not presumably af- 

 fected thereby. Very rarely the subject would come to the side 

 of the tank, in spite of the tendency of the light to turn it, and 



