Xenocrates of Chalcedon (396–314 B.C.), philosopher and mathematician, was a student of Plato and teacher of Epicurus {see, respectively, planets  (5451) and  (5954)}. As head of the Academy (339–314 B.C.) he upheld Plato’s policy that geometry and music are prerequisites to the study of philosophy. He wrote on the history of geometry and on number theory. (M 41034) _ _.