The Generation of Animals or (Greek: Περὶ ζῴων γενέσεως, Latin: De Generatione 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.
University of Adelaide (Internet Archive): On the Generation of Animals, translated by Arthur Platt, multiple formats.
Wikisource: On the Generation of Animals, translated by Arthur Platt, 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: The Generation of Animals.
The Great Conversation: Further reading at Tom's Learning Notes
Ancient Greek resources: Learn to read Greek classics in the original.