PREFACE ADVERSE circumstances had delayed the printing of this volume even before the war broke out. Thus the volume appears a year late. The work has in the main been compiled on the system followed in the earlier volumes. It is to be noted that for the first time the names of collections mentioned in the footnotes to the Comparative Table of Numbers at the end of the Rembrandt section have been included in the Index. This seemed desirable in view of the master's importance and the elaborate nature of the table and the footnotes. In preparing the Maes section the author has imposed on himself a restriction for the following reasons. The life-work of this painter falls into two parts, wholly distinct in style and quality the genre -pieces of his youth, which establish his fame and justify his appearance in this work ; and, on the other hand, the numerous portraits of his later life which in them- selves would not entitle him to a place here. To separate these categories was difficult if not impossible. For one thing, the author's precursor John Smith mentioned some of these later pictures ; again, there are numerous portraits both of the early period and of the period of transition which, as works of art, do not rank lower than many of the genre-pieces. One could not draw a line between these and the late portraits that should perhaps be ruled out. The author has therefore differentiated as follows.
