Fig. 1. Movement of a typical muscle preparation. The body is prepared by removing the head, viscera and a small portion of the dorsal musculature, and the skin is peeled away. EMG electrodes are inserted into muscles separated by approximately 15 segments. A small pin inserted through the notochord stabilizes lateral movement, but allows full rotation. Images were recorded on film at 15framess^-1, with every fifth frame illustrated. To construct the figure, outlines of the preparation in a selected single frame were used to form the shapes. One cycle is illustrated. Lines of equal length are drawn vertically from the pinned end for each image with the lines originating from the pin position.