Fig. 2. The percentage of macrostome cells that captured either deciliated Tetrahymena thermophila (grey columns) or latex beads with a diameter of 30 µm (stippled columns) in a medium containing (A) only deciliated T. thermophila, (B) only latex beads and (C) both deciliated T. thermophila and latex beads. The macrostomes consistently selected the cells rather than the beads. In all experiments, the concentration of the prey was 10⁶ ml^-1. The experiment was repeated three times, and 100 cells were counted in each experiment. Values are expressed as the mean + S.E.M.