The effects of 6-DMAP on assembly of microtubules and pronuclear migration between normal and gynogenetic fertilized eggs ofChlamys farreri were studied carefully by direct immunofluorescence with antitubulin. According to observation, chromosomes were segregated by spindle, the first and the second polar bodies were emitted and the female and the male pronuclei fused into zygotonucleus in normal eggs. Treatment of eggs at metaphaseanaphase stages caused drastic modifications of the spindle organization. The antitubulin staining revealed that soon after addition of 60μg/L l6-DMAP, outward astral fibers were no longer detected, whereas the spindle showed elongation and flattening. Finally 6-DMAP induced a significant disorganization of the spindle at the metaphase of meiosis II, the formation of the second polar body was inhibited effectively. The fertilized eggs raised in the presence of 6DMAP did not show any further pronuclear movements. when the treated eggs were washed and further maintained in fresh water ,migration resumed at a slower rate than in normal eggs.