THE MITOTIC FIGURE AND CLEAVAGE PLANE IN THE EGG OF PARECHINUS MICROTUBERCULATUS, AS INFLUENCED BY CENTRIFUGAL FORCE

Abstract

The mitotic figure of P. microtuberculatus may be shifted by centrifugal force to the centripetal pole, and the astral rays then become much elongate toward the centrifugal pole. In other batches of eggs it is thrown to the centrifugal pole and the astral rays then become elongate toward the centripetal pole. The 1st cleavage plane is correlated with the position of the nucleus or mitotic figure before centrifuging, and may bear no relation to its final position (primary plane). It is also correlated with the position of the nucleus or mitotic figure after centrifuging, since another cleavage plane may appear in relation to the new position of the figure (induced plane).