JÄGER, GUSTAV (1832- ), German naturalist and hygienist, was born at Bürg in Württemberg on the 23rd of June 1832. After studying medicine at Tübingen 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 polytechnic 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 und ihre Stellung zu Moral und Religion_ (1869), _Lehrbuch der allgemeinen Zoologie_ (1871-1878), and _Die Entdeckung 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 reproduction 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 offspring. In _Die Normalkleidung als Gesundheitsschutz_ (1880) he advocated the system of clothing associated with his name, objecting especially to the use of any kind of vegetable fibre for clothes. JÄGERNDORF (Czech, _Krnov_), a town of Austria, in Silesia, 18 m. N.W. of Troppau by rail. Pop. (1900), 14,675, mostly German. It is situated on the Oppa and possesses a château belonging to Prince Liechtenstein, who holds extensive estates in the district. Jägerndorf has large manufactories of cloth, woollens, linen and machines, and carries on an active trade. On the neighbouring hill of Burgberg (1420 ft.) are a church, much visited as a place of pilgrimage, and the ruins of the seat of the former princes of Jägerndorf. The claim of Prussia to the principality of Jägerndorf was the occasion of the first Silesian war (1740-1742), but in the partition, which followed, Austria retained the larger portion of it. Jägerndorf suffered severely during the Thirty Years' War, and was the scene of engagements between the Prussians and Austrians in May 1745 and in January 1779.