Rhythmicity of contraction of plasmodial strands of Physarum polycephalum was studied, by measuring the isometric tension exerted by isolated segments of the strands. When 2 strands were connected by way of a plasmodial mass, the contraction-relaxation cycle of the 2 strands synchronized. Such cycle activity of the strand was found to be well coordinated with shuttle streaming in the plasmodial mass which had been in connection with the strand. The presence of a control system which induces synchrony of periodic activity over the entire body of a plasmodium is discussed.

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