Kugler and his editor Eastlake systematically tackle the problem of who was responsible for which parts of the St. Peter cycle in the Brancacci Chapel. This is something which Ruskin, showing his impatience for Germanic art history (see Ruskin and Modern German art), calls wrong-headed. Ruskin against all the evidence attributed the whole cycle to Masaccio.
On the substance of the work Kugler stresses that it is only a beginning, and is more grudging in his praise than Vasari (compare Vasari on Masaccio and see Masaccio's Tribute Money):
The art of raising the figures from the flat, the modelling of the forms, hitherto only faintly indicated, here begins to give the effect of actual life. In this respect, again, these pictures exhibit at once a beginning and successful progress, for in the Tribute Money many parts are hard and stiff; the strongest light is not placed in the middle, but at the edge of the figures. ( Kugler, ed. Eastlake, Handbook of the History of Painting, Part One, The Italian Schools, First Edition, p. 108)