1. The interesting Prolegomena zu Aeschylus' Tragödien of R. Westphal (1869), which contains the germ of the idea worked out in Mezger's recent edition of Pindar, suggested to me to inquire why Aeschylus and the other pre-Sophoklean tragedians wrote tetralogies,—for this is the form in which Westphal's book suggests the question. But it becomes soon apparent that the real problem is why it was the habit to write a trilogy + a satyric drama; and this question contains two distinct parts: (1) why tragedy took the form of a trilogy— not a dilogy, tetralogy, or single drama; (2) why a satyric drama was also performed. Of these questions the latter has been discussed and adequately answered in every treatise on Greek drama.

Westphal was seriously misled through not keeping the satyric drama separate from the three plays that preceded it. These formed a connected whole and were really equivalent to one consecutive drama of three acts, from which the satyric piece was quite distinct, albeit its subject usually had some external connexion with them. He connected the tetralogical form with the fact first noticed by him that every Aeschylean play contains four χορικά, so that Aeschylus, he supposes, used a quadruple division as his artistic τϵθμός, in the same way as the Terpandric nomos was based on a seven-fold division.