Chromosomal passenger proteins slow anaphase spindle elongation. (A) Spindles were filmed as described in Materials and methods, and spindle lengths were measured at each time point. Each graph represents the mean spindle length for multiple cells (Table I), and the error bars in A indicate standard error. (B and C) Calculated spindle elongation rates and the standard deviations from the mean are shown for the indicated strains for phase I (B) and phase II (C). Statistical analyses were performed by comparing the wild type with each mutant (also see Table I).