"Richard III" and "Richard II," though possibly earlier than "King John," show the imitator and adapter rather than the reviser, and represent independent efforts to give tragic unity to the material of the English chronicles. While all the tragedies and histories so far considered have long since proved unfitted for the stage, "Richard III" has maintained its first popularity and continued to attract the greatest actors and to win the liking of the patrons of the theatre of each generation. Yet, though it has for three centuries exercised a profound impression on the popular imagination, it shows in the opinion of all critics a great indebtedness to Marlowe, and is so evidently imitative of current models that critics writing from such different points of view as Mr. Fleay and James Russell Lowell have been led to doubt Shakespeare's authorship. External and internal evidence both contradict such doubts emphatically, but the close relationship of the play to "Henry VI" makes it improbable that Shakespeare turned to the theme solely of his own initiative. "Richard III" is the fourth play of a tetralogy manifestly planned before the earlier members were completed. Margaret appears in all four plays; the character of Shakespeare's Richard is distinctly outlined in Part III; and it was evidently meant to end the contention of York and Lancaster with the triumph of the Tudor dynasty, and the long series of falls of princes with the tragedy of the villanous Gloster. The chronicle of Richard's reign had indeed been given a tragic unity in the history by Sir Thomas More and in a long saga of chronicle and literature which had developed still further the conception of this masterful and dreadful villain. The suitability of this material to current forms of tragedy was obvious. Dr. Legge had found in this saga the material for a Senecan play; the unknown author of "The True Tragedy" had discovered there a ready-made tragedy of blood and revenge; and there are indications of non-extant plays on the same theme. For either Marlowe or for Shakespeare working with him on the history of the struggle between York and Lancaster, the opportunity for a tragedy with a central hero of the type of Tamburlaine, Faustus, or Barabas must have been apparent.