Time spent in the light compartment of a petri dish containing water was quantified 0.25, 1 or 24 h following discontinuation of a 30-min exposure to frog extract (0, 0.0001, 0.001, 0.01 %). Data were presented as percentage of respective water control (i.e., percentage of water control time spent in the light compartment) + S.E.M. N=8–11 planarians/group. ***P < 0.001 or *P < 0.05 compared to water control (0 %).