. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. TIMING LIME FROBOSCIS Acnvrry FIGURE 3. Pressure (ordinate) in coelomic fluid and activity in Sipunculus nudus recorded with aid of metronome beat every third second. Timing line gives 10 second intervals. Con- ventions for record of proboscis activity as in figure 1 with addition 1 extended. 3 tentacles being we see, in several instances, one cycle of movements coinciding with two pressure cycles. The pressure cycle keeps firmly to its established timing, while the timing of the movement cycle is less constant; though keepi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. TIMING LIME FROBOSCIS Acnvrry FIGURE 3. Pressure (ordinate) in coelomic fluid and activity in Sipunculus nudus recorded with aid of metronome beat every third second. Timing line gives 10 second intervals. Con- ventions for record of proboscis activity as in figure 1 with addition 1 extended. 3 tentacles being we see, in several instances, one cycle of movements coinciding with two pressure cycles. The pressure cycle keeps firmly to its established timing, while the timing of the movement cycle is less constant; though keeping pace sometimes with the pressure cycle, at other times it is twice as slow. It should be noted that during what might be called an "extra-systole"-—a pressure cycle not coordinated with proboscis protraction—the pressure never rises as high as it does otherwise. Even in this case a certain relation between movement and pressure is, then, maintained; very high pressures seem to be set up only when proboscis protraction really occurs. PRESSURE CM of BODY FLUID iEROLINF--0- TINING LINE--. FIGURE 4. Sipunculus nudus, pressure and activity noted every fourth second with aid of metronome. Six second intervals on time line. Conventions for activity as in figure 3. The 5th and 6th pressure rises in Figure 2 are illustrations of this. Here pressure has no time to drop to the usual minimum, before the rise accompanying protraction occurs and the movement cycle is not exactly half as slow as the pressure cycle. Thus the rhythmicity of the pressure cycle is upset to some extent. Depend- ing on how soon after the "extra-systole" the large rise accompanied by proboscis protraction sets in, the "extra-systole" may be represented by a whole spike, as in Figure 1, or be reduced to a simple discontinuity of what appears to be one single pressure rise spike (6th spike on Figure 2). The pressure rise may set in before the formation of the hump. In this case the
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
