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Abstract

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).