(1) An epigentic process whereby the developmental fates of rates of cell development of embryonic subsystems may change during embryonic development, thereby compensating for defects and permitting normal development of the embryo as a whole. The human embryo is termed regulatory because its tissues and organs are not determined but become so according to the relationship of the different parts to each other. (2) In experimental embryology, the power of a pregastrula embryo to continue approximately normal development after a part or parts have been manipulated or destroyed. [L. regula, a rule]