Fig. 4

Swimming velocity and sedimentation velocity of worms during gravitaxis. Velocity of first day adult wild-type worms (N = 79) and of motion-impaired adult mutant unc-54 worms (N = 52) as functions of −cos θ, where θ = 0 corresponds to upward orientation. Since unc-54 does not swim, it only sediments. In contrast, the translational velocity of wild-type worms is a superposition of both sedimentation and swimming velocity (Eq. 3)