The exposure of new surface membrane occurred in the cleavage furrow of Rana amurensis eggs enclosed in fertilization membrane immersed in Brij solution. The exposed area increased gradually and reached a maximum while the furrow extended to 240 degrees around the egg surface. At this time, the new membrane area of the treated eggs was significantly larger than that of the control. Afterwards, the exposed new membrane area decreased gradually. This may result from the extent of new membrane increase being less than the extent of contraction of cleavage furrow.