This volume covers the culmination of Darwin's work on species. From early in 1856, when he was persuaded that the time had come to publish an account of his heterodox theories through 1857, Darwin's letters document the labor involved in composing his big species book, his zest for research, and his unflagging determination to succeed. As always, old friends and more recent acquaintances are drawn into the project. Darwin writes for the first time...