Abstract
NICHOLS in his recent restatements1,2 of the suture-line theory, has made out a strong case for the adaptive significance of pentameral symmetry in the newly metamorphosed echinoderm. Its admittedly transient advantages at this stage, however, do not seem to account for a pentamerous form persisting to determine the symmetry of the adult body. There are exceptions—Nichols1 quotes Promachocrinus—but why are they not the rule ?
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STEPHENSON, D. Pentameral Symmetry in Echinoderms. Nature 216, 994 (1967). https://doi.org/10.1038/216994a0
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DOI: https://doi.org/10.1038/216994a0
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