Maturation of the Ovum
The maturation of the ovum. A, An ovum at the commencement process. B, After the formation of the spindle. The chromosomes are gathered at the equator of the spindle in groups of four, i.e. in tetrads, each which consists of two dyads. C, One apex of the spindle has projected into a bud on the surface, and the dyads have passed to the poles. D, The separation of the first polar body. E, The commencement of the second polar body; F, The completion of the second polar body.