Pho·to·tax·is Pho·to·tax·y, n. Biol. The influence of light on the movements of low organisms, as various infusorians, the zoospores of certain algæ, etc.; also, the tendency to follow definite directions of motion or assume definite positions under such influence. If the migration is toward the source of light, it is termed positive phototaxis; if away from the light, negative phototaxis. -- Pho*to*tac*tic a. -- Pho*to*tac*tic*al*ly, adv.
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