Acis In the Greek mythology of Ovid, the son of Faunus (Pan) and the nymph Symaethis. Acis was a handsome shepherd of Sicily and the lover of the Nereid Galatea. His rival, Polyphemus the Cyclops, surprised them together and crushed Acis with a rock. His blood, gushing forth from beneath the rock, was metamorphosed by Galatea into a river bearing his name (Acis or Acinius--the modern river Jaci). Ovid is the only extant source for the tale.