trilogy were always connected; and whether he always produced his plays in trilogies, or sometimes also singly. Welcker thinks that, during his earliest period—down to perhaps about 490 B.C.—Aeschylus may sometimes have exhibited single plays; but that, after he had once adopted the trilogical form, he always connected the three plays, either by story (as in the case of the Oresteia), or by some pervading idea. Thus Welcker ingeniously supposes that, in the trilogy to which the Persae belonged, the connecting idea was Hellenic victory over the barbarian; the first play, called the Phineus related to the Argonauts; next came the Persae; and in the third piece, the Glaucus, the sea-deity of that name described the victory of the Sicilian Greeks over the Carthaginians at Himera in 480 B.C. Where the supposed link between the pieces is merely of this ideal kind, the group has been called a theme-trilogy; where the link is one of story (as in the Oresteia), a fable-trilogy. The doctrine of the theme-trilogy has been developed to the utmost extent by Adolf Schöll, in his Gründlicher Unterricht über die Trilogie (1859). He maintains that the law of inner unity in the trilogy was as strictly observed by the tragic poets after Aeschylus as, according to Welcker, it was by Aeschylus himself; and he attempts to show how the extant or recorded plays of Sophocles and Euripides can be grouped either by fable or by theme. More recently, G. Günther, in a work entitled Principles of the Tragic Art (1885) has advocated a view which
