Fig. 1. Schematic representation of the experimental setup. The horizontal x,y-plane is defined by an x-axis parallel to the lateral line, along which the position is denoted by s, and a laterally directed y-axis. A neuromast at position s is stimulated by a sphere placed at distance r and angle with respect to the x-axis. The distance of the sphere from the y-axis is denoted by b, and the distance from the x-axis (lateral line) by d. The sphere vibrates (double-arrowed bold line) at an angle relative to the x-axis, which corresponds to an angle between the axis of vibration and the vector pointing to the sphere position (r). For clearness, the geometry is depicted in relation to the trunk lateral line system. Actual measurements were done on the cephalic lateral line system.