Spindle rocking is correlated with large blebs. (A) There is no correlation between spindle length at cytokinesis onset and spindle rocking. (B) Increased cell length correlates with spindle rocking. (C) Spindle rocking is correlated with greater numbers of blebs of diameter ≥1 µm (P < 0.0001). (D) Increased numbers of large blebs correlate with rocking in anillin siRNA-treated cells (P < 0.0008). (E) There is a modest but significant difference in the time it takes for cells to begin rocking in anillin siRNA-treated cells versus MCAK siRNA-treated cells (P = 0.007). (D and E) Dotted lines indicate the mean. (F) The onset of rocking in a live HeLa cell treated with siRNA directed against anillin and coexpressing mCherry–α-tubulin (red) and GFP-Utr (green) is shown. Large blebs are indicated (arrows). Resolution (R) of a particularly large bleb precedes the onset of rocking. Asterisks indicate DNA. (G) Diagram summarizing the features (cell length and large blebs) in red that are associated with spindle rocking. Error bars indicate SEM.