In Experiments 7 tc 11^ colored bulbs were usedj, the 

 intensities of which were reduced to Oo1-Ilo8 foot candles 

 by placing a resistance in the circuito No attraction what- 

 ever was noted at these low intensities ^, 



In Sxperiments 12 and 13 j, the reaction of the fish to 

 intermittent light was compared at high and medium intensi- 

 ties o With 70 interruptions (on and off periods equal) per 

 minute, 530 foot candles-, there was no positive responseo 

 With 30 interruptions per minute (on and off periods equal) ^ 

 the tuna entered the field 3 times, whereas under control 

 conditions it did not enter at alio 



Series vi— Reactions to white and colored beams of light from 



proj 



ector 



As the results of the experiments in Series v suggested 

 that light over 500 or below ^0 foot candles is ineffective in 

 attracting the tunaj the present series was conducted with 

 white and colored light of moderate intensity (70 to 321; foot 

 candles) from the projector lanterno The intensity of the 

 beam was reduced by placing a resistance in the circuito One 

 yellowfin and five tunny were presento The results are shown 

 in table 7o. As indicated by the relatively large number of 

 entrances (6j 8^^ and 5) under control conditions j, the fish were 

 more active and restless than usual for some unknown reasono 



In Experiments 1 and 2, using continuous white light j 

 positive tropism was observed, as indicated by 9 and lU entran- 

 ces compared vn.th 6 under control conditions „ 



In Sxperiments 3 to 6, colored filters were placed across 

 the projector beanio Although Experiments 3 and k ware not con- 

 clusive, there seemed to be a definite tropistic reaction in 

 the duplicate Experiments $ and 6 with red and green filters, 

 as shown by 17 'd 10 entrances as compared with 8 under control 

 conditions o 



In Experiment 7, white light from the projector (32i4 foot 

 candles) was interrupted 72 times per minute (equal on and off 

 periods). The tuna entered the field 3 times., and were turned 

 away at the border ih times when the light changed. In Experi- 

 ment 8 with v^hita light from a 200-watt bulbj, similarly inter- 

 ruptedj the tuna entered the field 8 times as compared with 5 

 times under control conditions o 



52 



