Driesch, Hans Adolf Eduard (1867-1941)

German embryologist and philosopher who was one of the last advocates of vitalism, the theory that life is directed by a vital principle and cannot be explained solely in terms of chemical and physical processes. He made several important discoveries in embryology. Driesch was born in Bad Kreuznach, Prussia, and studied at the universities of Hamburg, Freiburg, Munich, and Jena. He travelled extensively in Europe and the Far East, working at the International Zoological Station in Naples, Italy, 1891-1900. He was professor of philosophy at Heidelberg 1911-20, moving to Cologne and Leipzig before being forced to retire 1935 by the Nazi regime. In 1891 Driesch, experimenting with sea-urchin eggs, discovered that the fate of a cell is not determined in the early developmental stages. Subsequently he produced an oversized larva by fusing two normal embryos, and in 1896 he was the first to demonstrate embryonic induction when he displaced the skeleton-forming cells of sea-urchin larvae and observed that they returned to their original positions. These findings provided a great impetus to embryological research. Driesch came to believe that living activities, especially development, were controlled by an indefinable vital principle, which he called entelechy.