Fig. 8. Period of dark field waves and persistence of cell movement in tsaca2 and DH1 at 22 and 28°C. (A) Periods of OD waves in mounds of DH1 and tsaca2 at 22 and 28°C. bar 1 is the period of DH1 at 22°C, bar 2 is the period at 28°C, bar 3 is tsaca2 at 22°C, bar 4 is tsaca2 at 28°C (where no waves were measured) and bar 5 is the period after return to 22°C. Data are means of at least three experiments. (B) Tracks of a fluorescently labelled DH1 cell at 22°C (solid symbols) and 28°C (open symbols) and the same for tsaca2 (C). The arrows show the direction of cell movement. The images were taken every 20 s; for clarity, the location of the centre of mass of each cell is shown every fourth image (80 s).