A.  In the Limulus eye, a plexus of axons connects the eccentric cell axons arising from the ommatidia.  Records from an axon extending from ommatidium X show that the axon generates the most spikes when it is illuminated alone: spikes are less frequent when ommatidium Y, X's neighbor, is also illuminated, and when ommatidia X, Y, and Z are illuminated.  (Limulus is a horseshoe crab)

B.  Firing frequency of a single eccentric cell in response to a sharp bright-dim edge moving in stepwise fashion across the ommatidial array of a Limulus eye.  Retinal distance is measured in numbers of ommatidia between the eccentric cell being recorded and the position of the edge.  Because of lateral inhibition, the differences in firing frequency of the cell were accentuated when the stimulus was adjacent to the cell being measured; differences in firing frequency were less extreme when the stimulus was some distance away from the cell (that is, approximately 10 ommatidia away).