ABSTRACT
Experiments on the influence of the polar lobe on the development of molluscs have shown that after removal of the polar lobe cleavage is radially symmetrical and indications of bilateral symmetry do not appear (Wilson, 1904: Dentalium;Clement, 1952: Ilyanassa). In normal development the polar lobe fuses with one of the two cells of the trefoil stage, and this cell becomes the posterior side of the embryo.
copyright © 1968 by Company of Biologists
1968
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