The extent of each monograph corresponds roughly to that of a chapter of the book. Accordingly, in order that there may be continuity between the book and its supplements, the monographs are called chapters and numbered consecutively with the chapters of the book. Chapters I — XIV are in the book; subsequent chapters are monographs. References from one part of the work to another are made by chapter and page numbers. Although the form of the book, and probably much of its authorship, will be changed, its purpose will remain unaltered. It is still intended, not for experts, but for students who, having taken the usual examination courses, wish to get into touch with research. It aims at giving them such knowledge of the chief regions in which research is active that they may proceed at once to the original memoirs; much more attention is therefore given to the clear exposition of the main ideas which inspire the research, than to detailed statements of the results that have been obtained from it. References to original literature are not given; for, if the book attains its object, the literature to which it is most important that the reader should turn is that which is not yet published.