WEISMANN, AUGUST (1834-1914), German biologist, was born at Frankfort-on-Main, on Jan. 17, 1834. In 1863 he went to Giessen to study biology under Leuckart, and in 1866 he was appointed extraordinary professor of zoology at Freiburg, becoming ordinary professor a few years later. His earlier work was largely concerned with purely zoological investigations, one of his earliest works dealing with the development of the Diptera. Microscopical work, however, became impossible to him owing to impaired eyesight, and he turned his attention to wider prob lems of biological inquiry. Between 1868 and 1876 he published a series of papers attacking the question of the variability of organisms ; these were published in an English translation under the title Studies in the Theories of Descent (1882), Darwin himself contributing a preface in which the importance of the nature and cause of variability in individuals was emphasized. Weismann's name is best known as the author of the germ-plasm theory of heredity, with its accompanying denial of the trans mission of acquired characters—a theory which on its publication met with considerable opposition, especially in England, from orthodox Darwinism. His views on the permanence of the germ
plasm and his rejection of the inheritance of acquired characters are not without their theological implications. A series of essays in which this theory is expressed and in which Weismann de clared that there must be a reduction division for the chromo some—a prophecy verified a few years later by Platner and others—was collected and published in an English translation (Essays upon Heredity and Kindred Biological Problems, vol. i. 1889, vol. ii. 1892). Weismann published many other works devoted to the exposition of his biological views. He died at Freiburg in Baden on Nov. 6, 1914. His latest publications were an estimate of Darwin's work, and Die Selektionstheorie.
For an account of his doctrines the reader is referred to the articles on HEREDITY, REGENERATION and REPRODUCTION, and CYTOLOGY. See also E. Gaupp, August Weismann (1917).