"In the year 1302," says Vasari, "Buffalmacco was invited to Assisi, where, in the church of San Francesco, he painted in fresco the chapel of Santa Caterina, with stories taken from her life. These paintings are still preserved, and many figures in them are well worthy of praise. Having finished this chapel, Buonamico was passing through Arezzo, when he was detained by the Bishop Guido, who had heard that he was a cheerful companion, as well as a good painter, and who wished him to remain for a time in that city, to paint the chapel of the episcopal church, where the baptistery now is. Buonamico began the work, and had already completed the greater part of it, when a very curious circumstance occurred; and this, according to Franco Sacchetti, who relates it among his Three Hundred Stories, was as follows. The bishop had a large ape, of extraordinary cunning, the most sportive and mischievous creature in the world. This animal sometimes stood on the scaffold, watching Buonamico at his work, and giving a grave attention to every action: with his eyes constantly fixed on the painter, he observed him mingle his colors, handle the various flasks and tools, beat the eggs for his paintings in distemper--all that he did, in short; for nothing escaped the creature's observation. One Saturday evening, Buffalmacco left his work; and on the Sunday morning, the ape, although fastened to a great log of wood, which the bishop had commanded his servants to fix to his foot, that he might not leap about at his pleasure, contrived, in despite of the weight, which was considerable, to get on the scaffold where Buonamico was accustomed to work. Here he fell at once upon the vases which held the colors, mingled them all together, beat up whatever eggs he could find, and, plunging the pencils into this mixture, he daubed over every figure, and did not cease till he had repainted the whole work with his own hand. Having done that, he mixed all the remaining colors together, and getting down from the scaffold, he went his way. When Monday morning came, Buffalmacco returned to his work; and, finding his figures ruined, his vessels all heaped together, and every thing turned topsy-turvy, he stood amazed in sore confusion. Finally, having considered the matter within himself, he arrived at the conclusion that some Aretine, moved by jealousy, or other cause, had worked the mischief he beheld. Proceeding to the bishop, he related what had happened, and declared his suspicions, by all which that prelate was greatly disturbed; but, consoling Buonamico as best he could, he persuaded him to return to his labors, and repair the mischief. Bishop Guido, thinking him nevertheless likely to be right, his opinion being a very probable one, gave him six soldiers, who were ordered to remain concealed on the watch, with drawn weapons, during the master's absence, and were commanded to cut down any one, who might be caught in the act, without mercy.