So far, then, evidence has been shown to prove Jan's share in the following pictures: the {41} _Chancellor Rolin_, the _Virgin and Child_ (at Dresden), the _Carthusian Monk_ in the Rothschild Collection, _St. Francis receiving the Stigmata_, _St. Anthony and the Donor_ (at Copenhagen), _The Three Marys at the Sepulchre_, the _Crucifixion_ (at St. Petersburg), the _Calvary_ (at Berlin), and the great altar-piece at St. Bavo, Ghent. Still another point which has been generally urged to prove collaboration of the two brothers is the appearance of their portraits in certain pictures. They are seen in the panel of the Ghent altar-piece representing the _Just Judges_, in the copy of the lost _Fountain of Life_ or _The Triumph of the Church over the Synagogue_ in the Madrid Museum, and also, it is said, in the _Crucifixion_ of St. Petersburg. Though the theory of collaboration is an old one, doubts have arisen amongst modern critics, who have shown a growing tendency to ascribe the majority of the unsigned works solely to the elder brother, which attribution is refuted not only by the arguments here set forth, but by many early writers, including Guicciardini and van Mander, both notable and reliable historians. Before leaving the question of collaboration, a few words must be said concerning the {42} controversy that has arisen over the Ghent altar-piece. This painting is indisputably the masterpiece of the van Eycks, and is of stupendous proportions. The panel of the _Adoration of the Lamb_, from which the whole alter-piece takes its name, and the shutters depicting the _Just Judges_, the _Warriors of Christ_, the _Holy Hermits_, and the _Holy Pilgrims_, have by many critics been attributed to Hubert's unaided efforts. It is therefore interesting to examine the landscape backgrounds of these five panels, and to consider them in the light of the evidence deduced from the backgrounds of the other "collaboration" pictures. Evidence is needed to prove that Jan's work was not merely confined to finishing the picture after his brother's death (the inscription states that it was begun by Hubert and finished by Jan), which in itself, of course, does not prove collaboration of the brothers.