from
The Collaborative International Dictionary of English v.0.48
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 zoospores 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.
[Webster 1913 Suppl.]