On the sarcophagus of Junius Bassus in the crypts of St. Peter’s, of date A. D. 359, are exhibited several scenes from scripture history, which will be hereafter described. In the spandrels of the arches over these is a series of bas reliefs, in which lambs are naively shown as enacting other scriptural scenes. In one a lamb, the personification of Moses, strikes a rock from which the water bursts forth, and another receives the law from the hand of God. Three lambs in a fiery furnace represent the three Hebrew children in the furnace of Nebuchadnezzar. Our Lord is symbolized by a lamb on whose head another, personifying John the Baptist, is pouring the waters of baptism, while the Holy Ghost in the form of a dove breathes divine 252 grace. A lamb, the personification of Christ, multiplies the loaves, and brings forth Lazarus from the grave. One of the most remarkable and important, in its theological significance, of the symbols of the Catacombs is that of the fish. It is one of the oldest in the entire hieratic cycle. It is found accompanying the first dated inscription which bears any emblem whatever,[403] and nearly a hundred examples occur which are attributed to the first three centuries. It was also one of the first to be discontinued. During the fourth century it rapidly fell into disuse, and by the beginning of the fifth had almost entirely disappeared from religious art.[404] The abandonment of this remarkable figure may be explained by its mysterious and anagrammatic character. It is a striking illustration of that _disciplina arcana_ of the primitive church which employed signs whose secret meaning its heathen foes could not understand. When the age of persecution passed away there was no longer the necessity to conceal under allusions and emblems, known only to the initiated, religious truths which were openly proclaimed on every hand. Hence this purely conventional sign fell into disuse. This symbol probably derived its origin from the fact that the initial letters of the names and titles of Our Lord in Greek--Ἰησοῦς Χριστὸς, 253 Θεοῦ Υἱὸς, Σωτήρ, Jesus Christ, Son of God, the Saviour--make up the word ΙΧΘΥΣ, a fish. “This single word,” says Optatus, “contains a host of sacred names.”[405] The same word also occurs acrostically in the initial letters of certain so-called Sibylline verses quoted by Eusebius[406] and Augustine,[407] which were doubtless of Christian origin. The symbol is first mentioned by Clement of Alexandria,[408] and probably had its origin in the allegorizing school of Christianity which sprang up in that city.[409]