The Aristotelian universe is eternal, not developing. Man begets man, for ever and ever. Professor Balme would adjure us to remember Libya, where individuals of differing species hybridize [1, 12]; still, this remains a small anomaly in a generally stable nature, in which species imitate the imperishable spheres by going round and round in their own imperfect way. Insofar as he is not an evolutionist, moreover, Aristotle's biological thought remains irreconcilably at odds with ours. Yet at the same time, while evolutionary thought, that is, in effect, Darwinism, remains the comprehensive framework for advancing biological knowledge, there is something in the philosophical foundations of modern thought that is disturbingly anti-biological and something in Aristotelian ontology that somehow seems better suited, if not to the practice of biochemistry, bioenergetics and the like, still to the pursuit of the more traditional branches of biology, which do still exist and on which in a sense their more sophisticated sister disciplines depend. This disparity makes me uncomfortable; I have tried a number of times to approach the question, what Aristotle has to teach the modern metabiologist, but the answer, perhaps the correct formulation of the question, still eludes me. Without much hope of succeeding better than before, let me try once again, relying chiefly on Aristotle's programmatic statements in P.A. I, together with some of his remarks about the τὶ ᾖν ϵἶναι and about form and matter in Met Z–θ.