Fig. 4. Mantle contractions frequency and fin-beat frequency for Lolliguncula brevis swimming against a steady current in a flume over a range of speeds in both tail-first and arms-first orientations. Data from four size classes are depicted: 1.0–2.9 cm, 3.0–4.9 cm, 5.0–6.9 cm and 7.0–8.9 cm dorsal mantle length (DML). When significant linear relationships were detected, regression lines were plotted, and regression equations, r2 values and P values were included underneath graphs. All error bars represent ±1 S.E.M. (N=3).