Lloyd Schwartz, on a touring exhibit of Venetian masterpieces from the National Gallery of Scotland making their way around the United States (currently in Minneapolis):  “Right now, two of Titian’s very greatest paintings — Diana and Actaeon and Diana and Callisto — are in the United States for the first time. … One reason I felt it was urgent to see them is that these two grand paintings are companion pieces, and there’s a chance they may be permanently separated.”