audience would have felt this to be necessary. Drama at the Dionysia was an act of religious worship. The honour of Dionysus was the central idea of the festival. The thing primarily required by Athenian feeling was not that the tragedies should be connected with each other, but that each should be worthy of the god. The unity of the tetralogy in this paramount aspect—viz., as a religious tribute—was symbolised by the number of the tragic Chorus. With Aeschylus, at least in his earlier period, the number was twelve; Sophocles raised it to fifteen by adding a coryphaeus (whose duties had formerly been taken by one of the ordinary choreutae) and two leaders of hemichoria; i.e. when the Chorus had to act in two equal divisions (as it does in a passage of the Ajax), these two men respectively led the two divisions. Both the older twelve and the later fifteen roughly represented one quarter of the old cyclic Chorus; and thus, though (so far as we know) the same twelve or fifteen men formed the Chorus in all the four pieces of a tetralogy, their number itself expressed the feeling that the tetralogy was a single performance.
Tetralogies continued to be exhibited throughout the fifth century B.C. The evidence for this rests ultimately on the basis of contemporary Athenian records. In the fifth century it was customary for the archon, after each occasion on which dramas had been performed, to draw up a list of the competing poets, the choregi, the plays, and the
