The Movement of Animals (or On the Motion of Animals; Greek Περὶ ζῴων κινήσεως; Latin De Motu Animalium) is a treatise by Aristotle.
Free online texts
Internet Archive: The works of Aristotle translated into English, Volume V. De Partibus Animalium, translated by William Ogle. De Motu and De Incessu Animalium, translated by A.S.L. Farquharson. De Generatione Animalium, translated by Arthur Platt. Multiple formats.
Internet Classics Archive: On the Motion of Animals, translated by A. S. L. Farquharson. HTML and TXT formats.
Loebulus. L323 - Aristotle -- Parts of Animals. Movement of Animals. Progression of Animals. PDF of public domain Loeb edition in Greek and English.
University of Adelaide (Internet Archive): On the Motion of Animals, translated by A.S.L. Farquharson. Multiple formats.
Wikisource: On the Movement of Animals, translated by A. S. L. Farquharson. Multiple formats.
History of Philosophy without any gaps: Classified Information: Aristotle's Biology - podcast by philosopher Peter Adamson.
Stanford Encyclopedia of Philosophy: Aristotle's Biology, by James Lennox.
Wikipedia: Movement of Animals.
The Great Conversation: Further reading at Tom's Learning Notes
Aristotle: History of Animals.
Ancient Greek resources: Learn to read Greek classics in the original.