A distance-dependent membrane furrow induction by the spindle midzone. (A) DNA bead-induced spindle formation at the center of an MII egg. (B) After inducing anaphase by SrCl2, the centrally positioned anaphase spindle was unable to induce membrane furrowing. Note that the cortically positioned maternal chromosomes and spindle (indicated by MII) induced the 2nd polar body extrusion (PbII). (C) The DNA bead-induced spindles were able to induce membrane furrowing and polar body extrusion (indicated by Pb) if positioned close to the cortex.