GUSTAV

JAGER (1832– )  , German naturalist and hygienist, was born at Burg in Wurttemberg on the 23rd of June 1832 . After studying medicine at Tubingen he became a teacher of zoology at Vienna . In 1868 he was appointed professor of zoology at the academy of Hohenheim, and subsequently he became teacher of zoology and anthropology at Stuttgart poly-technic and professor of physiology at the veterinary school . In 1884 he abandoned teaching and started practice as a physician in Stuttgart . He wrote various works on biological subjects, including Die Darwinsche Theorie and ihre Stellung zu Moral and Religion (1868), Lehrbuch der allgemeinen Zoologie (1871–1878), and Die Enideckung der Seele (1878) . In 1876 he suggested an hypothesis in explanation of heredity, resembling the germ-plasm theory subsequently elaborated by August Weismann, to the effect that the germinal protoplasm retains its specific properties from generation to generation, dividing in each re-production into an ontogenetic portion, out of which the individual is built up, and a phylogenetic portion, which is reserved to form the reproductive material of the mature off-spring . In Die Normalkleidung als Gesundheitsschutz (188o) he advocated the system of clothing associated with his name, objecting especially to the use of any kind of vegetable fibre for clothes .