Fig. 9. Movement of egl-4 mutant worms. N2 and the egl-4(ks61) worms were placed in an area at about 25°C on the gradient and observed for movement for 20 min. (A) Instantaneous velocities (filled circles) and their elements in gradient directions (open circles; positive values indicate upward movement; negative values indicate downwards movement) observed during the indicated period after the placement were averaged. After 10 min of the placement, N2 worms were excluded from a warm area above 24°C and no data was obtained above 24°C. Numbers of analysed intervals were as follows: N2: 0-5 min, 994; 5-10 min, 480; 10-20 min, 261; egl-4: 0-5 min, 1610; 5-10 min, 1148; 10-20 min, 890. (B) Examples of traces of the egl-4 worms. Time is indicated by the color scale.