of the behavior of the fish showed that with the plain bulb 

 the fish were attracted to the source, but with each abr'jpt 

 change between light and darkness, they were frightened 

 away if near the source, e„g,j near the south edge of the 

 fieldo Cn turning away from the light source, they swam 

 faster than usual and broke the school formation » Thu% the 

 tuna appeared to be attracted to lights of 106 and 2l5-can- 

 dle power when interrupted about once per second^ but were 

 repelled irvhen close to the stronger source^ by sudden inter- 

 nation or application of stimuli o 



Series i i i— Reactions to radiating light from bulbs 



In these experiments^ summarized m table kg an attempt 

 was made to repeat the results of Series ii, using the 

 painted 200-watt bulb and a 100-watt bulb of the same lumi- 

 nous intensity (10^ foot candles), and a 60-watt bulb with a 

 lower intensity (7C foot candles) » One yellowfin and five 

 tunny were present. 



Experiments 1 to U demonstrate a positive tropism to 

 continuous light at both intensities, thus confirming simi- 

 lar resiilts in Series ii„ In every case, the number of 

 entrances under experimental conditions was considerably 

 greater than under control conditions o 



In Experiments 5 to 9, the light was interrupted regu- 

 larly at various rates, and also irregular lyo In the latter, 

 the time of interruption was varied during the course of the 

 experiment to observe the effect of the change from light to 

 dark (and vice versa) on the pattern of movementc Fith the 

 100-watt bulb there was positive tropism at regular rates of 

 70 and 100-120 times per minute with the on and off periods 

 equal, and also with irregular rates j, with no appreciable 

 difference in the strength of the response between the regular 

 and irregular rates o Similarly there was positive tropism at 

 a regular rate o"" 6 times per minute, with the on period 0,5 

 and the off period 9o5 seconds c. These results confirm and 

 extend the obser'/ations included in Series ii, Mth the 60- 

 watt bulbj however, there was no definite attraction to irreg- 

 ular interrupted light, the tuna entering the field only twieeo 

 This lack of response is possibly associated with the low 

 intensity of the bulb (70 foot candles). 



Series iv— Reactions to radiating light from white and colored 

 bulbs of low intensity o 



In these experiments sources of light of smaller luminous 

 intensity than that of the overhead lights were used with con- 

 tinuous and intermittent stimulation,, One yellowfin and five 

 tunny were present. The results are given in table 5o 



