This book, a first attempt to survey and define the whole field of eugenics, appears in the year which finds us celebrating the centenary of the birth of Charles Darwin and the jubilee of the publication of The Origin of Species. It is a humble tribute to that immortal name, for it is based upon the idea of selection for parenthood as determining the nature, fate and worth of living races, which is Darwin's chief contribution to thought, and which finds in eugenics its supreme application. The book is also a tribute to the august pioneer who initiated the modern study of eugenics in the light of his cousin's principle. A few years ago I all but persuaded Mr. Galton himself to write a general introduction to eugenics, but he felt bound to withdraw from that undertaking, and has given us instead his Memories, which we could ill have spared.