E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Calisto and Arcas.
Calisto was an Arcadian nymph metamorphosed into a she-bear by Jupiter. Her son Arcas having met her in the chase, would have killed her, but Jupiter converted him into a he-bear, and placed them both in the heavens, where they are recognised as the Great and Little Bear.