Embryology was a subject that inspired great cross-disciplinary discussion in antiquity, and Plato’s Timaeus made an important contribution to this discussion, though Plato’s precise views have remained a matter of controversy, especially regarding three key questions pertaining to the generation and nature of the seed: whether there is a female seed; what the nature of seed is; and whether the seed contains a preformed human being. In this paper I argue that Plato’s positions on these three issues can be adequately determined, even if some other aspects of his theory cannot. In particular, it is argued that (i) Plato subscribes to the encephalo-myelogenic theory of seed, though he places particular emphasis on the soul being the true seed; (ii) Plato is a two-seed theorist, yet the female seed appears to make no contribution to reproduction; and (iii) Plato cannot be an advocate of preformationism.
For Alcmaeon see CensorinusDe dei nat.5.4 (= 24A13 DK) and 6.4 (= 24A14 DK). Hippon is sometimes described as having advanced a one-seed theory on the basis of 38A14 DK and Censorinus De dei nat. 5.4 but Aëtius Plac. phil. 5.5.3 (= 38A13 DK) attributes a theory of female seed to Hippon though this seed does not contribute to the embryo as it is not conducted to the uterus as in Herophilus. See Lesky Zeugung 28 and below on the female seed in Plato. For other references to the Pythagoreans see Diogenes Laertius Vit. phil.8.28 (= 58B1 DK); Aëtius Plac. phil.5.5.1; and L. Zhmud Pythagoras and the Early Pythagoreans (Oxford 2012) 374–80. For Parmenides see 28B18 DK; Aëtius Plac. phil. 5.11.2 (= 28A54 DK); Censorinus De dei nat. 5.4; 6.5; and 6.8 (the latter two passages are included in 28A54 DK). For Empedocles see 31B63 DK. Cf. 31A81 DK. For Democritus see Aëtius Plac. phil. 5.5.1 (= 68A142 DK); Aristotle GA 764a6–11 Drossaart Lulofs (= 68A143 DK) and P.-M. Morel “Aristote contra Démocrite. Sur l’embryon” in L. Brisson M.-H. Congourdeau and J.-L. Solère eds. Porphyre. Sur la manière dont l’embryon reçoit l’âme (Paris 2008) 43–57 at 46ff. For Epicurus see Aëtius Plac. phil. 5.5.1. For the Hippocratics see especially Genit. and Nat. Puer. and Lonie Hippocratic Treatises 119–122. Also Mul. i 8 (8.349f.; 8.5621f.; and 8.6220f. Littré) and Vict. i 27 (1444–5 Joly = 6.5008f. Littré). For Diocles see Fr. 42a/b in P.J. van der Eijk Diocles of Carystus. A Collection of the Fragments with Translation and Commentary 2 vols (Leiden 2000–2001) = Fr. 172 in M. Wellmann Die Fragmente der sikelischen Ärzte Akron Philistion and des Diokles von Karystos (Berlin 1901). Cf. Lesky Zeugung 30. For Herophilus see Galen De sem. 14620–14824 De Lacy (= 4.5964- 5987 Kühn and T60 von Staden) but also note 5 below. For Soranus see Gyn. 1.4.93–98 Burguière et al. Regarding Galen see especially De sem. 2.1 (1444 - 16023 De Lacy = 4.5931–61010 Kühn) and D. Nickel Untersuchungen zur Embryologie Galens (Berlin 1989) 40–49.
Regarding Alcmaeon see AëtiusPlac. phil.5.5.3 and Censorinus De dei nat. 5.2 (both are included in 24A13 DK). Censorinus testifies that Alcmaeon actually opposed the encephalo-myelogenic theory but as Lesky Zeugung 12 points out this is simply due to his “ungenaue Sammelberichterstattung.” For Hippon see Censorinus De dei nat. 5.2 (= 38A12 DK); Aëtius Plac. phil. 5.3.3 (= 38A13 DK). For more general evidence of Pythagoreans holding this view see Diogenes Laertius Vit. phil. 8.28 (= 58B1 DK) and the note ad loc (905A) in Lachenaud Plutarque. There are traces of this view in the Hippocratic corpus at e.g. Genit.1.2 (4410–20 Joly = 7.4708–16 Littré). In general see Lesky Zeugung 13–18; Lonie Hippocratic Treatises 101–3; von Staden Herophilus 288–96. For Diocles see Fr. 41a-b van der Eijk.
E.g. LeskyZeugung18–20; E. Lesky and J.H. Waszink “Embryologie” Reallexikon für Antike und Christentum 4 (1959) 1228–1244 at 1228; F.M. Cornford Plato’s Cosmology: The Timaeus of Plato translated with a running Commentary (London 1937) 295; van der Eijk Diocles of Carystus vol. 2 92; M.-H. Congourdeau L’embryon et son âme dans les sources grecques (Paris 2007) 197.
Cf. Theophilus ProtospathariusDe corp. hum. fabr.5.3.1 (1895–8 Greenhill) where the brain is described as a “field” in which the rational soul is planted either directly or by means of the spinal marrow.
AëtiusPlac. phil. 5.3.6 (= 68A141 DK): Δημόκριτος ἀφ’ ὅλων τῶν σωμάτων καὶ τῶν κυριωτάτων μερῶν οἷον ὀστῶν σαρκῶν καὶ ἰνῶν [τὸ σπέρμα εἶναι]. There is some disagreement about whether the first καί is meant to be epexegetic (thus Perilli “Democritus” 171) or co-ordinative (H. De Ley “Pangenesis versus panspermia. Democritean Notes on Aristotle’s Generation of Animals” Hermes 108  130–153 at 135–6). In the former case we have homoiomerous pangenesis the results for the latter interpretation will depend on how one understands ἀφ’ ὅλων τῶν σωμάτων (which De Ley takes to refer to the organs).