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PACIFIC SCIENCE, Vol. XV, April 1961 
highly significant at 15 ft. c. and 30 ft. c. How- 
ever, at 70 ft. c, the worms acclimated to a 
white background showed no preference when 
tested on contrasting backgrounds. The worms 
acclimated to the black background continued 
to orient to the black background when tested 
on contrasting backgrounds. It was postulated 
that the change in response at 70 ft. c. of animals 
acclimated to the white background was a re- 
sult of crossing a threshold of light sensitivity 
so that the more sensitive animals tended to 
orient to the black background while the less 
sensitive animals tended to orient to the white 
background. 
6. The capture of a copepod prey is described. 
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