The locomotory movements of a typical polychaete worm, such as Nereis diversicolor, are of interest in that they are effected by two distinct mechanisms, (i) a series of parapodia which act as levers comparable to the appendages of terrestrial animals, (ii) the longitudinal muscles of the body. When Nereis is moving slowly over a solid surface, only the parapodia are active; during more rapid motion, or when the animal is swimming through water, the movements of the parapodia are co-ordinated with those of the longitudinal muscles and the two mechanisms combine to give a highly co-ordinated locomotory mechanism.

Copyright © 1939 The Company of Biologists Ltd.
1939
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