. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 542 K. OHTSU AND M. YOSHIDA razor. The responses in Figure 7B, C and D were evoked by three successive stimuli (B to D) delivered at intervals of sec. The left column shows records with the subumbrellar muscle side up, the mesogloea side being applied to the indifferent electrode. The SSP's showed waveforms similar to those of intact tissues. The increased positivity of the first phase both in amplitude and in the falling phase which appeared in response to the 3rd stimulus (D, left) was often observed after several
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 542 K. OHTSU AND M. YOSHIDA razor. The responses in Figure 7B, C and D were evoked by three successive stimuli (B to D) delivered at intervals of sec. The left column shows records with the subumbrellar muscle side up, the mesogloea side being applied to the indifferent electrode. The SSP's showed waveforms similar to those of intact tissues. The increased positivity of the first phase both in amplitude and in the falling phase which appeared in response to the 3rd stimulus (D, left) was often observed after several repetitive stimuli. The recordings of the right column were done after the same preparation was turned over, and the electode was re- positioned in the site corresponding to that in the previous recordings. It is note- worthy that the first phase, being positive on the left, became negative on the right and that in D, the increased positivity of the first phase on the left reflected as the increase in negativity on the right. On the other hand, the polarity of the second phase, being only positive in this case, did not alter in spite of the changes in the waveforms. Pulses on the ectoderm and the endodcnnal lamella It has been described in some hydromedusae that the exumbrellar ectoderm and the subumbrellar endoderm are completely nerve free, but that conductive pulses are recordable from them (Mackie and Passano, 1968). Figure 8A and B shows pulses evoked on the exumbrella by electrical stimuli. They were usually diphasic with amplitudes of mV (A), and sometimes showed a notch in the course of the deflection (B), suggesting the existence of multiple components. Con- duction velocities were measured at 16-21° C, using 6 animals and 2 measure- B D fp. FIGURE 8. Epithelial pulses (EP's) and endodermal pulses (EDP's). A and B show EP's recorded on the exumhrella. C and D are records obtained by successive stimuli on the intact subumbrellar muscle sheet, show
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