"On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection" is the name of a journal article that includes two scientific papers that were jointly presented to the Linnean Society of London on July 1st, 1858. The piece also includes an introduction by Joseph Dalton Hooker and Charles Lyell, as well as an abstract of a letter that Darwin wrote to Asa Gray. The Darwin-Wallace hypothesis of evolution through natural selection was initially introduced in the paper, which first appeared in print on August 20, 1858. Darwin was inspired by the papers' presentations to create an abbreviated "abstract" of his "huge book" on Natural Selection. On the Origin of Species, a version of this was released in November 1859.