Some tri-polar cells organize midzone microtubules between two of the three pairs of spindle poles. Typically one set of midzone microtubules move and merge with other midzone microtubules. Ingression takes place only between the poles with midzone microtubules, causing the cell to divide into two. In this cell no ingression occurs in the upper region. These observations suggest that the site of ingression is defined by the distribution of midzone microtubules. Recording time, 23 min. |