The "Life and Letters of Charles Darwin" was published in 1887. Since that date, through the kindness of various correspondents, additional letters have been received; among them may be mentioned those written by Mr. Darwin to Mr. Belt, Lady Derby, Hugh Falconer, Mr. Francis Galton, Huxley, Lyell, Mr. John Morley, Max Muller, Owen, Lord Playfair, John Scott, Thwaites, Sir William Turner, John Jenner Weir. But the material for our work consisted in chief part of a mass of letters which, for want of space or for other reasons, were not printed in the "Life and Letters." We would draw particular attention to the correspondence with Sir Joseph Hooker. To him Mr. Darwin wrote with complete freedom, and this has given something of a personal charm to the most technical of his letters. There is also much correspondence, hardly inferior in biographical interest, with Sir Charles Lyell, Fritz Muller, Mr. Huxley, and Mr. Wallace. From this unused material we have been able to compile an almost complete record of Mr. Darwin's work in a series of letters now published for the first time. We have, however, in a few instances, repeated paragraphs, or in one or two cases whole letters, from the "Life and Letters," where such repetition seemed necessary for the sake of clearness or continuity...