Eggs were cut before fertilization either in the equatorial plane or parallel to it; the membrane was not entirely severed after the egg was cut, so as to reduce injury to the segments. Polar halves of Chaetopterus eggs divide unequally, but without formation of the yolk lobe. Antipolar halves divide unequally with a proportionately small lobe. Lobe formation is therefore not a necessary part of the unequal cleavage pattern, nor is the size of the lobe determined as if by a fixed amount of "material." The relation is discussed of the "pear-shaped" stage and of lobe formation to size and position of the mitotic figure.