Abstract(1)Aplysia californicaexhibit a diurnal circadian locomotr rhythm (Strumwasser, '67). The rhythm appears to be timed by circadian pacemakers located within the eye, although extraocular photoreceptors and pacemakers also influence locomotor behavior (Strumwasser, '73; Lickey et al., '77). (2) The present study was undertaken in an attempt to identify the pathways ganglia, which are responsible for generatating locomotor movements. A lesion study was performed in which either of the two pairs of bilaterally symmetrical cerebral connectives were cut and the effect on locomotor behavior evaluated. (3) The results indicate that the cerebro‐pleural connectives are not involved in control of locomotor acitivity (Fig. 2). On the other hand, the cerebro‐pedal connectives are critical for ocular and extraocular control of locomotor thythmicity (Figs. 3,4). Animals with bilateral cerebropedal lesions are arrhythmic on light cycles. (4) Multiunit recording in vivo and in vitro revealed the presence of a descending signal in the cerebropedal connective upon the application of a light pulse to the animal. Further experimentation localized the origin of these signals to the tentacles, rhinophores and eyes (Figs. 6, 7). (5) We conclude that the elements comprising the circadian system ofAplysiaare located in a restricted portion of the central nervous system including the cerebral and buccal ganglia, and sensory structures served by cerebral or buccal ner