 "Closed" and "open" mitosis can be distinguished on the basis of nuclear envelope remaining intact or breaking down.An intermediate form with partial degradation of the nuclear envelope is called "semiopen" mitosis.With respesct to the symmetry of the spindle apparatus during metaphase, an approximately axially symmetric (centered) shape is called as "orthomitosis", distinguished from the eccentric spindles of "pleuromitosis", in which mitotic apparatus has bilateral symmetry.