Historically embryogenesis has been among the most philosophically intriguing phenomena. In this paper I focus on one aspect of biological development that was particularly perplexing to the ancients: self-organisation. For many ancients, the fact that an organism determines the important features of its own development required a special model for understanding how this was possible. This was especially true for Aristotle, Alexander, and Simplicius, who all looked to contemporary technology to supply that model. However, they did not all agree on what kind of device should be used. In this paper I explore the way these ancients made use of technology as a model for the developing embryo. I argue that their di ff erent choices of device reveal fundamental di ff erences in the way each thinker understood the nature of biological development itself. In the fi nal section of the paper I challenge the traditional view (dating back to Alexander's interpretation of Aristotle) that the use of automata in GA can simply be read o ff from their use in the de motu.