Regulative development in the pulmonate gastropod, Lymnaea palustris, as determined by blastomere deletion experiments

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Abstract
To determine the regulative ability of Lymnaea eggs one or more cells were deleted by puncturing or shaking eggs at the 2−, 4−, 8− and 16‐cell stages. Normal snails developed from: one/two, three/four, and two/four embryos; from 8‐cell embryos in which one, two, or three cells of the first quartet of micromeres or one or two macromeres were deleted; and from 16‐cell stage embryos in which one cell of the second quartet of micromeres or one macromere was deleted. Only one/two embryos that cleaved as though they were whole eggs up to the 24‐cell stage developed normally. Normal development of other partial embryos was associated with partial cleavage. Developmental abnormalities of partial embryos included death in the cleavage period; arrested gastrulae; trochophores, or veligers; and abnormal snails with head malformations, everted stomodea, or conical shells.Comparing the results with deletion experiments in other molluscs and with deductions from descriptive studies on the Lymnaea egg, we propose that the regulative ability of partial embryos depends on the rearrangement of cells relative to the D macromere before inductive activities begin at or after the 24‐cell stage.