Hair cell responses to adequate stimulation of statocyst, eye and chemoreceptors of the optic tentacle bulb were studied by means of intracellular and extracellular recordings. Hair cells increased firing frequency to titling of the statocyst. Displacement of the statocyst caused a depolarizing wave with superimposed spikes in the hair cell. This depolarizing wave or generator potential increased in proportion to magnitude of displacement. The onset of a light flash and the illumination of eye photoreceptors caused a short-latency (0.3-2 s) increase in the firing frequency of hair cells. The latency of the response was in reversed proportion to the light intensity. Adequate stimulation of chemoreceptors of optic tentacle bulb caused a long-latency (20-40 s) discharge response in the hair cell. In some cases adequate stimulation of photoreceptors and chemoreceptor pathway caused inhibitory responses in 2 of above 50 hair cells.