We may put the case, then, without further reliance on the evolution of physical species. For three hundred years Englishmen have been writing tragedies, all much alike, all related in origin, nature, and purpose. In our study of their relationships, the influences governing their creation have been grouped in two main classes: first, that of the theatre itself, and second, that which has been called the literary tradition. In the theatre has been included the influence of actors and audience and all pertaining to the theatrical presentation. Changes in the mere stage and its appurtenances have been factors determining the very nature of tragedy. The scenery and women actors of the Restoration compelled important modifications in the drama; the large theatres of Kemble's day drove tragedy from the stage and encouraged a pantomime hybrid. The influence of theatrical fashions and traditions, always in part changing and transitory, has been felt in every variation, advance, or retrogression of the acted drama. Yet it is the influence of the theatre that has maintained the integrity of form and has thus been the main force in preserving the species. The literary tradition, even more complex in its elements than that of the theatre, altering and cumulative, composed of classical or French as well as English masterpieces, drawn from the novel or other forms as well as the drama, affected by all social movements, passing through such transformations as those of the classical and the romantic periods, has nevertheless, on the whole, conserved the form and content of tragedy. During the periods that we have examined, blank verse, illustrious persons, the pomp of courts, the great passions of revenge, ambition, jealousy, lust, love, and hate, hideous crimes, and the conflict of potent wills have been the usual accompaniments of the actions of suffering and ruin. There has been only occasional departure from the Shakespearean conception of tragedy as representation of great personalities engaged in disastrous conflict. Shakespeare, in fact, at least since Dryden's "All for Love," has been a constant and often the dominating element in this complex and variable literary tradition. The two classes of influence, theatrical and literary, have thus proved both variable and conserving. The theatre, while crying for novelty, holds tenaciously to its traditions. Literature, while enforcing rules, precedents, prejudices, while clinging to its models and demanding imitation, yet incites to rivalry and originality, to new endeavor, variation, and excellence.