phototaxis, n. [NL. phototaxis; photo- + Gr. an arranging.].
The influence of light on the movements of low organisms, as various infusorians, the zoöspores 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. [Webster 1913 Suppl.]