Fig. 3. Blastula cells align the spindle with an experimentally induced long axis. (A) Round isolated blastomeres were compressed and filmed to assess the orientation of the cleavage plane with respect to the introduced long axis: parallel (spindle perpendicular to the long axis), perpendicular (spindle parallel to long axis) and oblique (orientation between these two categories). Arrowheads indicate cleavage planes. (B) Cleavage plane orientations were analysed with respect to the time that has elapsed between mechanical deformation and cytokinesis (n=100 divisions). The shorter the elapsed time between deformation and cytokinesis (0-3 minutes, 3-5 minutes), the smaller the percentage of spindles that align with the long axis. When a long axis is imposed 5-15 minutes before cytokinesis, the spindle aligns with it in 100% of cases. The correlation between division type and time, measured to the nearest half minute, was highly statistically significant (Spearman's correlation -0.647, n=100).