Discussion of Greek accentuation for plural/genitive forms: -ες (εἰς) often give barytone over two syllables, comparison with -ις and -υς forms, Attic proparoxytone tendencies, examples (Αἴαντες, ἑβδομάδες, εὐσεβέες), Aristarchus' opinion, perispomena vs barytone alternations.
Αἱ εἰς 'ες' ὑπὲρ δύο συλλαβὰς εὐθεῖαι βαρύνουσι τὰς γενικάς, Αἴαντες Αἰάντων, ἑβδομάδες ἑβδομάδων, εὐσεβέες εὐσεβέων, στάχυες σταχύων, ὀσφύες ὀσφύων. ἔδει οὖν καὶ τὸ πόλεων, μάντεων, πελέκεων καὶ τὰ τούτοις παραπλήσια πρὸ μιᾶς ἔχειν τὸν τόνον. ἀλλ´ Ἀττικούς φασι προπαροξύνειν ταῦτα, ἅπερ ἐστὶν ἀπὸ τῶν εἰς 'ις' εὐθειῶν, καὶ ἔτι δύο ἀπὸ τῶν εἰς 'υς', τό τε πήχεων καὶ πελέκεων. σεσημείωται πάλιν γυναικῶν καὶ θυγατρῶν περισπώμενα ἑπόμενα τῷ τόπῳ τοῦ τόνου τῆς γενικῆς ἑνικῆς καὶ τὰ παρ´ Ἀθηναίοις ἀριθμητικὰ τὸ χιλιάδων καὶ μυριάδων. ταῦτα γὰρ παρ´ αὐτοῖς περισπῶνται, παρ´ ἡμῖν δὲ βαρύνονται. Αἱ δὲ εἰς 'εις' εὐθεῖαι συνῃρημέναι εἰσὶ καὶ περισπῶσι τὰς ἰδίας γενικάς, ὡς ἤδη εἴπομεν, Σωκράτεις Σωκρατῶν, Δημοσθένεις Δημοσθενῶν, εὐσεβεῖς εὐσεβῶν. τὸ δυσώδων καὶ εὐώδων καὶ νοσώδων τῷ λόγῳ μὲν περισπασθήσονται, ὁ δὲ Ἀρίσταρχος ταύτας καὶ τὰς ὁμοίας βαρύνει ἐκ τοῦ οἴεσθαι τὰς ἐντελεῖς γενικὰς αὐτῶν προπαροξύνεσθαι, εὐώδεων ὡς πόλεων. οὐκ εὐλόγως· μόναι γὰρ αἱ ἀπὸ τῶν εἰς 'ις' ὑπάρχουσιν αἱ προπαροξυνόμεναι, πόλεων, μάντεων, καὶ δύο ἀπὸ τῶν εἰς 'υς' πελέκεων, πήχεων, αἱ δὲ λοιπαὶ πᾶσαι βαρύτονοι οὖσαι πρὸ μιᾶς ἔχουσι τὸν τόνον, ὡς πρόκειται. παραλόγως οὖν Ἀρίσταρχος βαρύνει καὶ ἐπείσθη ἡ παράδοσις. καὶ τὸ τριήρων οἱ μὲν βαρύνουσιν, οἱ δὲ περισπῶσιν, ὥσπερ καὶ αὐτάρκων καὶ αὐθάδων καὶ τὸ συνήθων καὶ κακοήθων βαρύνεται ὥσπερ καὶ τὰ αὐτῶν ἐπιρρήματα.
Nominatives in -ες of more than two syllables make their genitives barytone: Αἴαντες Αἰάντων, ἑβδομάδες ἑβδομάδων, εὐσεβέες εὐσεβέων, στάχυες σταχύων, ὀσφύες ὀσφύων. Accordingly, πόλεων, μάντεων, πελέκεων and the like ought also to have the accent on the penult. But they say that the Attics accent these with a proparoxytone, since they are derived from nominatives in -ις, and further two from those in -υς, namely πήχεων and πελέκεων. Again, γυναικῶν and θυγατρῶν are noted as circumflexed, following the position of the accent of the singular genitive, as also among the Athenians the numerals χιλιάδων and μυριάδων. For among them these are circumflexed, whereas among us they are barytone. Nominatives in -εις are contracted and circumflex their own genitives, as we have already said: Σωκράτεις Σωκρατῶν, Δημοσθένεις Δημοσθενῶν, εὐσεβεῖς εὐσεβῶν. δυσώδων and εὐώδων and νοσώδων will, according to the rule, be circumflexed; but Aristarchus makes these and the like barytone, on the supposition that their full genitives are proparoxytone, εὐώδεων like πόλεων. Not reasonably: for only those derived from -ις are proparoxytone—πόλεων, μάντεων—and two from -υς, πελέκεων, πήχεων; but all the rest, being barytone, have the accent on the penult, as has been stated. Therefore Aristarchus accents them barytone contrary to rule, and the tradition was persuaded. And τριήρων some accent barytone, others circumflex, just as also αὐτάρκων and αὐθάδων; and συνήθων and κακοήθων are accented barytone, just like their corresponding adverbs.