Alfred Russel Wallace is best known as the co-originator of the theory of evolution by natural selection, an honor he shares with his contemporary Charles Darwin. Among the ten essays in this volume is his seminal paper on natural selection, On the Tendency of Varieties to Depart Indefinitely from the Original Type, which was presented with Darwin’s On the Origin of Species at a meeting of the Linnean Society of London in July 1858. This edition of Wallace’s Contributions to the Theory of Natural Selection is the first entry in the Foundations of Biological Thought series published by Briar Bird Press. The series presents the pivotal works of 19th century naturalists remastered for modern readers. Meticulously edited, these volumes preserve the author’s intent in design and content, including the manuscript’s original annotations and amendments. In addition, revised page references and editor’s notes are included throughout to retain the utility of the works for both study and reference.