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1. Nine hundred and sixty cat retinal ganglion cells were evaluated with respect to receptive‐field organization and latency to antidromic activation of their axons from optic‐tract and mid‐brain positions.

2. The vast majority (92%) had the familiar concentric centre/surround organization. As in earlier work these could be classed as sustained or transient, independently of the centre type. About 13% of the concentric cells were characterized by relatively sluggish responses to conventional visual stimuli which yielded brisk responses from the others. The sluggish cells constituted a previously unspecified class of concentric receptive fields.

3. The responses of brisk and sluggish cells to a variety of stimuli were described with a view to developing procedures for distinguishing them on functional grounds.

4. Measurements of latency to antidromic activation of retinal axons confirmed earlier work in showing that cells …