. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 188 J- BUCK AND J. F. CASE between two populations, one peaking between 700 and 1000 ms, the other concen- trated inly below 300 ms (7B). The overall record included several quite uniform rur or more consecutive SIRs in the 1100 to 1200 ms latency range and a like runs of 10 or more consecutive S2Rs in the 700 to 850 ms range, so there , little doubt that there do exist valid photic responses to both SI and S2. It also ins safe to conclude from Figure 7 that any flash that follows a signal by more than 2000 ms is not a respo
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 188 J- BUCK AND J. F. CASE between two populations, one peaking between 700 and 1000 ms, the other concen- trated inly below 300 ms (7B). The overall record included several quite uniform rur or more consecutive SIRs in the 1100 to 1200 ms latency range and a like runs of 10 or more consecutive S2Rs in the 700 to 850 ms range, so there , little doubt that there do exist valid photic responses to both SI and S2. It also ins safe to conclude from Figure 7 that any flash that follows a signal by more than 2000 ms is not a response but a spontaneous emission. 7. Further S1R/S2R interrelations. Implication of spontaneity. In many experiments, under a variety of conditions, only S2Rs occurred. The latencies of these thousands of responses averaged 650-950 ms and were almost never shorter than 600. There is thus a priori reason to suspect that the 50 to 600 ms apparent S2R latencies in the above SIR-rich experiment (Fig. 7B) were not conventional re- sponses to S2. A few flashes might have been spontaneous emissions that fell fortuitously within SIR or S2R latency ranges, but we believe most belonged to one or other of the following two effects, neither of which involved true S2Rs. Because of the 400 ms minimal central nervous delay (Introduction) the short latency responses in Figure 7B could not have been evoked by S2s. Assuming that central delay was often longer than 400 ms, many could have been SIRs. Thus (Fig. 8) any SIR excitation in which the centrally delayed fraction (CND) had been com- pleted, and motor excitation (M) had started on its way to the lantern before the S2 signal arrived, would evoke a flash that could be misinterpreted as a short la- tency S2R. The other phenomenon that almost certainly contributed to the spurious short- latency S2Rs of Figure 7B was the marked tendency for Female 62's flashes to occur in pairs about 1500 ms apart (Fig. 9). In about a third of the 90 such pairs r
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