THE PRIMARY aim of this book is to explain the remarkable rule which regulated the succession to the priesthood of Diana at Aricia. When I first set myself to solve the problem more than thirty years ago, I thought that the solution could be propounded very briefly, but I soon found that to render it probable or even intelligible it was necessary to discuss certain more general questions, some of which had hardly been broached before. In successive editions the discussion of these and kindred topics has occupied more and more space, the enquiry has branched out in more and more directions, until the two volumes of the original work have expanded into twelve. Meantime a wish has often been expressed that the book should be issued in a more compendious form. This abridgment is an attempt to meet the wish and thereby to bring the work within the range of a wider circle of readers. While the bulk of the book has been greatly reduced, I have endeavoured to retain its leading principles, together with an amount of evidence sufficient to illustrate them clearly. The language of the original has also for the most part been preserved, though here and there the exposition has been somewhat condensed. In order to keep as much of the text as possible I have sacrificed all the notes, and with them all exact references to my authorities. Readers who desire to ascertain the source of any particular statement must therefore consult the larger work, which is fully documented and provided with a complete bibliography.