Epigenesis

Epigenesis, a technical name for the modern conception of the development of the organism by the growth and differentiation of a simple germ—i.e. by the division or segmentation of a fertilised egg-cell. This conception, now a commonplace, was first definitely enunciated by Harvey (1651), and was reasserted with cogent demonstration by Wolff in 1759, in opposition to the generally received theory that the germ contained a pre-formed miniature model of the organism which only required to be unfolded. See EMBRYOLOGY.