Results are reported here from experiments in which single unit neural activity was recorded simultaneously from the optic nerve and connective of the crayfish Procombarus clarkli to study functional connections between units responding to movement in visual space. The single unit data was analyzed through computer generated plots of poststimulus time histograms, interspike interval histograms, autocorrelation plots, joint peristimulus time histograms and normal and shifted crosscorrelation plots. In three experiments, discussed here in detail, evidence was obtained for strong functional connections between optic nerve motion detectors and connective motion detectors. In two other experiments, evidence was obtained for strong functional connections between the connective motion detectors and units in the other two classes of crayfish optic nerve visual units: the sustaining units and the dimming units.