Fig. 5. Measurement and models of N. bachei swimming trajectory. The ratio of instantaneous forward motion (relative to its position at the start of the measured swimming cycle) to the maximum forward motion, x/X_max, is plotted versus the current point in the full swimming cycle (i.e. ejection and relaxation). Both the real animal (solid black line) and the model that includes transient velar kinematics (broken black line) achieve continuous forward motion, whereas the model that assumes a constant velar aperture (dotted grey line) swims backward during the latter portion of the swimming cycle. Measurement uncertainty is ±3%.