Regulative Egg

the egg of deuterostomes (except ascid-ians) and some protostomes, characterized by comparatively late differentiation of various regions of the cytoplasm and by more or less even distribution of its component parts. Upon division of the blastomeres (including artificial division), an entire embryo of diminished size may develop in the early stages of cleavage from each blastomere or group of blastomeres. However, such regulation of a part to a whole only occurs if the divided blastomeres contain all parts of the cytoplasm; if a blastomere is separated that does not contain all its components, it gives rise, as do the blastomeres of mosaic eggs, only to part of the embryo’s body.