JAGER, GUSTAV (1832-1917), German naturalist and hygienist, was born at Burg, Wurttemberg, on June 23, 1832. After studying medicine at Tubingen he became a teacher of zoology at Vienna. In 1867 he was appointed professor of zoology at the academy of Hohenheim, and subsequently he became teacher of zoology and anthropology at Stuttgart polytechnic and professor of physiology at the veterinary school. In 1884 he aban doned teaching and started practice in Stuttgart. In 1876 he anticipated Weismann's germ-plasm theory by suggesting that the germinal protoplasm retains its specific properties from genera tion to generation, dividing in each reproduction into an onto genetic portion, from which the individual arises, and a phylo genetic portion, reserved to form its reproductive material. In
Die Normalkleidung, als Gesundheitsschutz (188o, 4th ed. 1885), he advocated the system of clothing associated with his name, objecting especially to the use of vegetable fibre for clothes. He died at Stuttgart on May 14, 1917.
Jager's other works include: Die Darwinsche Theorie (1869), Lehr buch der allgemeinen Zoologie (1871-78), and Die Entdeckung der Seele (1878) ; Selbstarznei im Heilmagnetimus (1908) and Leben im Wasser (3rd ed. 2908).