Professor Robertson rejected recent proposals to substitute the name of some other animals (e.g. cats) for eagles in Plutarch, Mor. 520F (ὥσπερ γὰρ οἱ ἀετοὶ καὶ οἱ λέοντες ἐν τῷ περιιπατεῖν συστρέϕουσιν εἴσω τοὺς ὄνυχας) by reference to Aristotle's statement (H.A. 563 a 17, echoed by Pliny, N.H. x, 3 (4) and Horapollo II, 99) that eagles' claws are distorted during incubation. He suggested that either οἱ ἀετοὶ καὶ is a reader's interpolation based on Aristotle, or <ἐν τῷ ἐπῳάЗειν καὶ> has been lost between οἱ λέοντες and περιπατεῖν.