Fig. 2. Swimming direction and pattern of 60 intact larvae in the x—y plane. Each point in the x—y plane shows the final position (x_f, y_f) of the intact larvae after swimming from the initial position at the origin (0, 0). Different symbols denote the different patterns of swimming exhibited by the larvae, i.e. straight (open circle), spiral (open triangle), curved (solid circle) and random (solid triangle). Most of the intact larvae collected within 3h of hatching swam upward. The shaded area represents 45° from the y axis (see Fig. 5).