On natural selection - Darwin, Charles, 1809-1882. (New York : Penguin Books, 2005)
Struggle for existence -- Natural selection -- Difficulties on theory -- Conclusion.
"This extract first published in Penguin Books (U.K.) 2004."--T.p. verso.
"Taken from the Penguin Classics edition of The origin of Species, edited by J.W. Burrow"--T.p. verso.
Keywords: Evolution (Biology); Natural selection