On Proteus, see Verg. "Georg." iv. 387 sq.; Ovid, "Art." i. 761; "Met." ii. 9; "Fasti," i. 367 sq., and especially Horace, "Epistles," i. i. 90: "Quo teneam vultus mutantem Protea nodo?"
Literally, "having no hearth of character," the hearth being an emblem of stability. Compare "How One may Discern a Flatterer from a Friend," § vii., where the same image is employed.