German biologist and master experimenter who was one of the leading practitioners of Entwicklungsmechanik. When he discovered that almost any cell had the ability to become an embryo, however, he set out to destroy Entwicklungsmechanik, challenging the mechanistic view and reviving Vitalism Theory. Driesch performed a series of experiments which refuted the theory of Weismann and Wilhelm Roux, which stated that nuclear divisions were responsible for the organization of a developing embryo. Driesch repeated Roux's experiment by agitating sea urchin cells during division and causing them to fragment. Instead of forming a partial embryo as Roux had reported, however, Driesch found that the cells formed an entire one. Furthermore, using pressure, he forced developing cells to arrange themselves in unusual patterns, and noticed that he still got an normal individual.

Weismann, Roux (Wilhelm)