In a dense passage of GA II,6, 745a4-10 Aristotle tackles the question of why, even though animals keep on nourishing themselves, they do not grow on without end. As childlike as this query may seem, the answer given in the passage is admittedly partial. Further, it requires Aristotle to take into account a rather complex network of topics, whose detailed study is, moreover, announced as forthcoming in his lost (or never written) writings on nutrition. These topics include, on the one hand, a fine-grained distinction between different parts and uses of nutriment and residues, and, on the other hand, an analysis of the relationships between growth and form, shape and size, essence and limit, outline and structure. In order to reconstruct the theoretical framework of what may have been Aristotle’s fuller answer, then, we shall explore a number of passages of his psychological and biological works.