Fig. 2.

Quantitative analysis of the movies: results. (A) Two-dimensional embedding of a stroke plotted against video frame number, showing the shape and pace uniformity of the stroke over several realizations. Isomap identifies similar shapes from different realizations (here about four cycles) and yields a single geometric stroke. (B) Pseudo-time parameter τ against normalized physical time t during three full strokes represented in different colors, showing that path in shape space is traveled with a well-defined pace (here, euglenid #3). The black line shows the fit used to reparameterize time. (C) Reduced volume, v, as a function of time during two strokes. We distinguish two distinct motility styles: a volume-changing style for euglenids #1 and #2, and a volume-preserving style for euglenids #3 and #4. See Fig. S3 for the full data.