Optimal amounts of cross-linker and motor activity are required for maximal actomyosin contraction in simulated and real cortex. (A) Representative Cytosim simulations of the cortex with differing amount of motor and cross-linkers. From top to bottom, the number of motor/cross-linkers are: 0:2; 0:32; 64:2; 64:32; 64:64; 64:128 thousands. (B) Quantification of time required from anaphase onset to the completion of cytokinesis in control (n = 19) and plst-1 overexpression (n = 25) zygotes. Data are represented as mean ± SEM. **, P < 0.01, by Mann–Whitney U test.