Radial cleavage

From Freepedia

Radial cleavage is a cleavage pattern characteristic of some animal groups, for instance vertebrates and echinoderms, in which the spindle axes are parallel or at right angles to the polar axis of the oocyte. In most other groups, such as annelids and mollusks, embryos undergo spiral cleavage, in which the cleavage planes are oriented obliquely to the polar axis of the oocyte.