On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection.

Lyell and Hooker’s own letter of introduction explaining the extraordinary circumstances; 2. An excerpt from Darwin’s unpublished draft, part of a chapter titled, “On the Variation of Organic Beings in a State of Nature; on the Natural Means of Selection; on the Comparison of Domestic Races and True Species”; 3. An abstract of Darwin’s 1857 letter to Harvard University botanist, Prof. Asa Gray; 4. Wallace’s manuscript, “On the Tendency of Varieties to Depart Indefinitely From the Original Type.”