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Fig. 2 Dynamics of migration speed. A: Kymograph of a migrating primordium, illustrating the progressive slowing down of the proneuromasts. Deposition was arbitrarily taken as the time when Vt reaches 65% of Vl. At this stage, the speed of the trailing cells was renamed Vp (speed of the proneuromast cells). B: Outline of the primordium and neuromasts corresponding to the kymograph in A, to illustrate the different phases of deposition. The center of each rosette is represented by a black dot. C: Spatial distribution of mitoses for different ratios of Vt (speed of the trailing cells) or Vp (speed of proneuromast cells) over Vl (speed of the leading cells). Ratios were expressed as %. Time-lapses were divided in stretches corresponding to the different Vt/Vl and Vp/Vl intervals given at the left. Each line corresponds to the length of a primordium (except for the lowest one, see below). Black bars indicate the position of the mitoses recorded during the corresponding interval. On the right are shown the cumulated duration of all stretches (minutes), and the total number of mitoses recorded for each interval. The lowest bar corresponds to the stage where the trailing cells are moving at a speed lower than 65% of the leading cells, that is, when a proneuromast is effectively separating from the primordium. The separation between primordium and proneuromast is represented by a break in the line. The rightmost part of the bottom line, therefore, corresponds to the primordium length, that is, to the whole length of all other lines.