What is "phototaxy"

Phototaxis \Pho`to*tax"is\, Phototaxy \Pho"to*tax`y\, n. [NL. phototaxis; photo- + Gr. ? an arranging.] (Biol.) The influence of light on the movements of low organisms, as various infusorians, the zo["o]spores of certain alg[ae], 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.