Frederick Burkhardt (1912–2007), the founder of the Darwin Correspondence Project, was president of Bennington College, Vermont, 1947–1957, and president of the American Council of Learned Societies, 1957–74. Before founding the Darwin Correspondence Project in 1974, he was already at work on an edition of the papers of the philosopher William James. He received the Modern Language Association of America's first Morton N. Cohen Award for a Distinguished Edition of Letters in 1991, the Founder's Medal of the Society for the History of Natural History in 1997, the Thomas Jefferson Gold Medal of the American Philosophical Society in 2003 and a special citation for outstanding service to the history of science from the History of Science Society in 2005. James A. Secord has served as Director of the Darwin Correspondence Project since 2006. He is Professor of History and Philosophy of Science at the University of Cambridge and a fellow of Christ's College. Besides his work for the Darwin Project, his research focuses on the history of science from the late eighteenth to the early twentieth centuries. His book, Victorian Sensation: The Extraordinary Publication, Reception, and Secret Authorship of Vestiges of the Natural History of Creation (2000), won the Pfizer Prize of the History of Science Society.

Review of volumes 19 and 20: 'The editing and organization of these volumes is, as always, superb; the Darwin Correspondence really does set the standard against which all comparable projects have to be measured. In addition to a wonderfully erudite editorial apparatus (the footnotes alone contain a wealth of invaluable information), all the surviving letters Darwin received are published … as well as by dates, topics and so on … the importance and usefulness of these volumes go well beyond the world of Darwin, or even studies of the many forms of nineteenth-century evolutionism. No Victorianist should be without them.' Jim Endersby, British Journal for the History of Science

• List of illustrations; List of letters; Introduction; Acknowledgments; List of provenances; Note on editorial policy; Darwin/Wedgwood genealogy; Abbreviations and symbols; The correspondence; Appendixes: 1. Translations; 2. Chronology; 3. Diplomas presented to Charles Darwin; 4. Presentation list for Descent; 5. Reviews of Descent; 6. Henrietta Emma Darwin's journal, 1871; 7. Darwin's Queries about expression; Manuscript alterations and comments; Biographical register and index to correspondents; Bibliography; Notes on manuscript sources; Index.