. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 35 36 37 FIGURES 31-37. 48-hour larvae treated for the first 24 hours with M/160,000-A//320,000 zinc chloride and then returned to sea water. posure was continuous. In high (A//10,000-Af/20,000) and intermediate (A//40,- 000-Af/SO,000) concentrations for 24 hours there was radial symmetry and polar elongation but with apical and basal lobes developing and differentiating. Stomo- daea also appeared in these experiments which may indicate that the factors re- sponsible for such differentiation are not very sensitive to inhibit
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 35 36 37 FIGURES 31-37. 48-hour larvae treated for the first 24 hours with M/160,000-A//320,000 zinc chloride and then returned to sea water. posure was continuous. In high (A//10,000-Af/20,000) and intermediate (A//40,- 000-Af/SO,000) concentrations for 24 hours there was radial symmetry and polar elongation but with apical and basal lobes developing and differentiating. Stomo- daea also appeared in these experiments which may indicate that the factors re- sponsible for such differentiation are not very sensitive to inhibition during the first 24 hours. The appearance of the stomodaeum at the apical end may indicate a part of the phenomenon of ventralization in which the ventral area extends more rapidly than the dorsal and in this case pushes the stomodeal region apically. 4. Exposure of nrid-blastulae to zinc chloride for six and eighteen hours Whereas six hours exposure to high concentrations of zinc chloride, beginning immediately after fertilization, gave only over-all inhibition and lower concentra- tions had little or no effect the situation was quite different when the 6-hour blastula was exposed for a similar period. Six hours exposure to Af/10,000-A//20,000 gave 75-90 per cent radial elongated forms (Figs. 38-41) with thin apical regions or lobes. The remainder graded into inhibited bilateral plutei (Figs. 42-45). Some of these were radial and enlarged apically but bilateral basally (Figs. 42, 43). In Af/20,000, most of the bilaterals had skeleton and most of the elongated radials had rings of skeletal spicules around their bases (Figs. 40, 41). No exogastrulae were found. Approximately 60 per cent of the blastulae exposed for six hours to M/40,000 developed into bilateral forms (as Figs. 42-45), commonly elongated in the polar direction (Figs. 42-44) but with short anal arms. The remaining 40 per. Please note that these images are extracted from scanned page images that may have been d
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
