In 198, when the difference between Asia and the rest of the Church concerning Easter came under discussion, an exchange of letters took place between the leading authorities of the Church, Pope Victor, Bishop Narcissus of Jerusalem, Polycrates of Ephesus, Bacchylus of Corinth, Irenæus, and others taking part. Irenæus composed a special treatise _De Paschate_, sometimes called _De Schismate_, unfortunately lost. In the fragments falsely attributed to him, Easter is referred to in the third and seventh. References to Easter are frequent in Tertullian. With regard to the name, it is to be noticed that with him _pascha_ denotes, not the single day of the Easter festival, but a longer period of time, in which a fast was observed and baptism administered,[84] in other words, Passion-tide and the Easter Octave.[85] Moreover, for the actual day of our Lord’s death, he uses the word, _parasceve_.[86] The festival of Easter, as he further relates, was kept in the first month (_i.e._ March),[87] and was prefigured by the Jewish Passover.[88] We possess a treatise on Easter, of the year 243 A.D., formerly attributed wrongly to St Cyprian, but, probably, a translation of work of Theophilus of Cæsarea. It is entitled _De Paschate Computus_, and was written elsewhere than at Rome, in the interest of the Easter cycle of sixteen years drawn up by Hippolytus. The remarks of Hippolytus on the Quartodecimans afford us important evidence for the Ante-Nicene period. “These,” he says, “agree with the Church in preserving all the apostolic traditions, but differ from her in one point, inasmuch as, out of contentiousness, wilfulness, and ignorance, they maintain that the Christian feast must always be kept on the 14th Nisan, no matter on what day of the week it falls.”[89] If the Arabic Canons ascribed to Hippolytus, especially the twenty-second, are really his, it would appear that he held Easter might be kept in the same week as the Jewish Passover, but on the Sunday, and should be preceded by a week’s fast on bread and water.[90] This date coincides with the Easter cycle of sixteen years drawn up by Hippolytus, and which, after all, is only the Jewish cycle of eight years doubled. The seventh and sixty-ninth of the so-called Apostolic Canons refer to Easter and its preparatory fast. The seventh is also important on account of what it says about the period within which Easter may fall: “Whosoever keeps Easter with the Jews before the vernal equinox, let him be anathema.” From which it appears that the Jewish Passover could fall before the vernal equinox. The last day of Nisan alone must never precede the equinox, and, consequently, the Passover must frequently have fallen before the 21st March, and may have done so in the year of our Lord’s death.