1. Intracellular recordings were made from cells in medullae of immobilized, intact flies Calliphora erythrocephala. Stimuli were moving gratings or small spots projected onto translucent hemispheres before the fly.--2. Responses to stationary flashes included tonic and phasic slow potentials only. Sustaining and On/Off discharges were recorded from cells silent in the dark. Sustaining, dimming, On/Off, +On-Off, and-On/-Off discharges were recorded from cells spontaneous in the dark (Fig. 1, 2, and 3).--3. Some cells were relatively sensitive to 3 log unit changes in flash intensities; others were insensitive (Fig. 4).--4. Receptive fields of a few cells tested were small-field ipsilateral monocular, large-field ipsilateral monocular, or large-field binocular.--5. A number of types of nondirectional cells were found. Some gave stronger discharges to movement than to stationary flashes (Fig. 5).--6. Directionally-selective cells were generally spontaneous. Some simply fired faster in the preferred direction. Others (Fig. 6) had inhibition in the null diriction with or without hyperpolarizations.--7. Possibly-new nondirectional cells were found that were inhibited by changes of direction of movement (Fig. 7)--8. A number of cells were stained with Procion yellow, using high voltage pulses. Double stainings sometimes occurred (Fig. 8).