In De Partibus Animalium I Aristotle sets out his philosophy of biology, discussing cause, necessity, soul, genus, and species, definition by logical division, and general methodology. In De Generatione Animalium I he applies his hylomorphic philosophy to the problem of animal reproduction. The translation is close, and includes passages from De Generatione Animalium II which complete Aristotle's theory of reproduction. The notes interpret Aristotle's arguments and discuss his views on major issues such as natural teleology. "These additions increase the usefulness and extend the life of an already indispensable introduction to the theoretical underpinnings of two of Aristotle's most challenging scientific treatises."-- Bryn Mawr Classical Review "A most welcome publication, like all previous items in the Clarendon Aristotle series."--Roberto Torretti, University of Puerto Rico In 'De Partibus Animalium I' Aristotle sets out his philosophy of biology, discussing cause, necessity, soul, genus and species, definition by logical division, and general methodology. In 'De Generatione Animalium I' he applies his hylomorphic philosophy to the problem of animal reproduction. This volume also includes passages from 'De Generatione Animalium ll' which completes Aristotle's theory of reproduction. The translation is close, in order to serve the needs of readers of Aristotle without a knowledge of Greek; the notes interpret Aristotle's arguments and discuss his views on major issues such as natural teleology. This edition is brought up to date by the inclusion of a wide - ranging report on recent work and a large additional bibliography. D. M. Balme is at Queen Mary College, University of London. Allan Gothelf is at Trenton State College, New Jersey.