. The Biological bulletin. Biology; Zoology; Marine biology. 514 R. A. SATTERLIE AND J. F. CASE. Figure 19. Full view of a primary polyp. Xl4, medium squash. Two siphonozooids are visible (arrows). settled for an hour or more. If the larvae are not allowed to settle, the late swimmer stage is prolonged and further morphological changes, such as tentacle budding, are delayed. Muscular activity. Obvious muscular activity is lacking until the swimmer stage (60 hr), after elongation is underway. At this point a mechanical or electrical stimulus to any part of the planula produces a local contracti
. The Biological bulletin. Biology; Zoology; Marine biology. 514 R. A. SATTERLIE AND J. F. CASE. Figure 19. Full view of a primary polyp. Xl4, medium squash. Two siphonozooids are visible (arrows). settled for an hour or more. If the larvae are not allowed to settle, the late swimmer stage is prolonged and further morphological changes, such as tentacle budding, are delayed. Muscular activity. Obvious muscular activity is lacking until the swimmer stage (60 hr), after elongation is underway. At this point a mechanical or electrical stimulus to any part of the planula produces a local contraction which pulls the stimulated tissue away from the probe. This muscular contraction is not conducted circularly or longitudinally. Within 2 to 5 hr, similar stimuli produce a more widespread circular constriction, and the planulae contract longitudinally to about two thirds of the relaxed length. At this time, the septa are well formed (Fig. 7). By the late swimmer stage, the larvae are capable of bending movements as well as "protective" longitudinal contractions. These conducted muscular events are not observed when the planulae are placed in excess Mg++ for 5 min. In the anesthetized state, stimulation only produces local twitches as in the earlier planulae. At the time of planula attachment, a division between polyp and peduncle re- actions is evident. A stimulus to the peduncle produces a conducted contraction, but not always with an accompanying polyp contraction. Similarly, polyp stimula- tion does not always produce peduncular contractions. As soon as tentacle buds. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-; Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woo
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