Latencies were calculated from the onset of the shortening stimulus. These data are from semi-intact preparations with the stimulating electrodes implanted between segments 3 and 4. The sample sizes are small because it was often difficult to determine the precise start of PSPs in swim circuit cells, which can show spontaneous variations in membrane potential; thus, precise latency values could not be obtained from all of the cells tested. It was uniformly clear, however, in all of the cells 204, 208, 61, and 115 tested that the latencies were <100 msec. For cases in which n = 1, that value is given in the mean column. The range is given as minimum, maximum.