This class comprises drafts of the nine surviving chapters of a large manuscript known as 'Natural Selection', which although only partially complete was effectively the precursor to 'On the origins of the species'. Darwin's progress on the manuscript was 'interrupted' by the arrival of Alfred Russell Wallace's paper, June 1858. The manuscript was published posthumously by R. C. Stauffer in 1975 as 'Charles Darwin’s Natural Selection, Being the second part of his big species book written from 1856 to 1858'.

The volumes comprise: table of contents, completed drafts for chapters 3-10, incomplete draft of chapter 10, and material relating to chapter 4.