August Weismann (1834-1914) was a German biologist best known as the originator of the germ-plasm theory of heredity (the idea that a special hereditary substance constitutes the only organic continuity between one generation and the next). He achieved distinction through his zoological investigations, notably on the embryology of insects and crustaceans. Weismann was the first scientist to reject as unproven the then prevalent but incorrect doctrine accepted by the French naturalist Jean de Lamarck and others that characteristics acquired during the lifetime of a individual may be transmitted to the offspring.