LEEUWENHOEK or LEUWENHOEK, ANTHONY VAN (1632-1723), Dutch microscopist, was born at Delft on Oct. 24, 1632, and died there on Aug. 26, 1723. For a time he was in a merchant's office in Amsterdam, but soon turned to the manu facture of microscopes and to the study of the minute structure of organized bodies by their aid. He found that single lenses of very short focus were preferable to the compound microscopes then in use, and though his researches were not conducted on any definite scientific plan, his powers of careful observation enabled him to make many interesting discoveries. He extended M. Mal pighi's demonstration of the blood capillaries in 1668, and six years later gave the first accurate description of the red blood corpuscles. In 1677 he described and illustrated the spermatozoa in dogs and other animals, though in this discovery Stephen Hamm had an ticipated him by a few months ; and investigated the structure of the teeth, crystalline lens, muscle, etc. In 168o he noticed that
yeast consists of minute globular particles, and he described the different structure of the stem in monocotyledonous and dicoty ledonous plants. The first representation of bacteria is to be found in a drawing by Leeuwenhoek in the Philosophical Transactions of the Royal Society in 1683.