 Although Hays would claim in his autobiography that the examination of Bryan was unplanned, Darrow spent the night before in preparation.The scientists the defense had brought to Dayton—and Charles Francis Potter, a modernist minister who had engaged in a series of public debates on evolution with the fundamentalist preacher John Roach Straton—prepared topics and questions for Darrow to address to Bryan on the witness stand.Kirtley Mather, chairman of the geology department at Harvard and also a devout Baptist, played Bryan and answered questions as he believed Bryan would.