Stoic biology made a distinction between nature and soul, classifying natural bodies into soulless plants and ensouled animals. The clearest influence of this classification, starting from the third century B.C., was in its embryological claim that the foetus, being directed by nature, is not an animal, a Stoic innovation upon Platonic and Aristotelian biology. The mid-second-century A.D. Stoic Hierocles reaffirmed this in his brief account of embryology, but, apart from textual difficulties raised by the surviving papyrus of his book, the question arises: does nature cease or remain in the animal after birth? More specifically, should the animal's faculties of nutrition and growth be classified as parts of soul after this has been formed? It appears that the Stoics' debate about the issue to some degree turned on concepts of competing divisions of the soul's parts or faculties. Unfortunately, insufficient textual evidence remains to illuminate their debate; and how the debate was conducted by Stoics from Panaetius on is uncertain, despite some secondhand reports that may help us to reconstruct it. Our one relevant late Stoic source is the opening of Hierocles' book, but he is entirely silent on it in his ensuing treatment of embryology. 1 Even some degree of doxographical disagreement exists on the issue. Calcidius, at In Platonis Timaeum 220, reports a Stoic doctrine, attributed to Chrysippus, that the animal's nutrition and growth are taken over by the parts of soul after birth. 2 Galen, at Adversus Iulianum 5, and ps.-Galen, at Introductio 13 (that the latter refers to the Stoics is hardly in doubt), cite another Stoic doctrine, that the animal is governed both by nature and by soul (see below). Under the circumstances, it is hard to determine whether this disagreement was actually one between the historical Stoics, or merely reflects a doxographical divergence in transmission, and whether Chrysippus differed from the other Stoics on the issue. Moreover, the question whether (and if so how) those two Stoic doctrines are fully compatible needs closer scrutiny. Below I shall argue that the Stoics held to a belief in the continuation of nature in the animal, and that any impression of a disagreement, on this view, is likely to derive from Calcidius' misreporting. Even if Calcidius were right to attribute to Chrysippus the opinion that the soul's parts include provision for nutrition and growth in the animal, it would be probable that this opinion belonged at best to Chrysippus and some Chrysippeans. But 97