normally celebrated in private houses or in secret places such as catacombs. The catacombs (networks of underground passages and caves) in Rome contain many of the surviving works of Christian art from this early period. Several of them portray the Eucharist. The earliest, from the late second century, is to be found in the catacomb of Saint Callistus. Christ is symbolized as a fish: the letters that make up the Greek word for fish, ICHTHUS, were taken to represent I(esus) Ch(ristos) Th(eou) U(ios)