Embryos derived from sstn^EY06542/Df(3L)BSC441 females show defects during cellularization. Pseudocleavage and cellularization furrows extend effectively into the embryo as in controls, but then the membranes undergo abnormal perpendicular expansion from the base of the furrows. The expanded membranes are coated with a cytoskeleton marker (pnut) and are seen to encroach into the space normally occupied by the nuclei, resulting in nuclei with indentations and bottle-like shapes.