Figure 8.

Spiral swimming. A, Organization of ciliary basal bodies on the oral (ventral) and aboral (dorsal) side (from Iftode et al., 1989, with permission). B, Ciliary beat cycle: power stroke (or effective stroke) and recovery stroke (Omori et al., 2020). C, Water currents produced by cilia for different orientations of Paramecium (Jennings, 1904). In the oral groove, currents are oriented toward the mouth. D, Metachronal waves represented by parallel lines, progressing transversally, with cilia’s power stroke oriented toward the right and rear (from Machemer, 1972, with permission). Cilia on parallel lines are at the same phase of the beat cycle. The curved arrow shows the direction of movement.