The origin of species by means of natural selection :
or the preservation of favored races in the struggle for life /
by Charles Darwin ; with additions and corrections from sixth and last English edition.

APA Citation

Darwin, C. (1898). The origin of species by means of natural selection: or the preservation of favored races in the struggle for life. Authorized ed. New York: D. Appleton.

MLA Citation

Darwin, Charles, 1809-1882. The Origin of Species by Means of Natural Selection: Or the Preservation of Favored Races In the Struggle for Life. Authorized ed. New York: D. Appleton, 1898.

Warning: These citations may not always be complete (especially for serials).