Chicago: Charles Darwin, "Chapter 2," Life and Letters of Charles Darwin, Vol. 2, ed. Darwin, Francis and trans. Babington, B. G. (Benjamin Guy), 1794-1866 in Life and Letters of Charles Darwin Original Sources, accessed February 15, 2025, http://www.originalsources.com/Document.aspx?DocID=JP4FIHBESMTMZ74.
MLA: Darwin, Charles. "Chapter 2." Life and Letters of Charles Darwin, Vol. 2, edited by Darwin, Francis, and translated by Babington, B. G. (Benjamin Guy), 1794-1866, in Life and Letters of Charles Darwin, Vol. 2, Original Sources. 15 Feb. 2025. http://www.originalsources.com/Document.aspx?DocID=JP4FIHBESMTMZ74.
Harvard: Darwin, C, 'Chapter 2' in Life and Letters of Charles Darwin, Vol. 2, ed. and trans. . cited in , Life and Letters of Charles Darwin. Original Sources, retrieved 15 February 2025, from http://www.originalsources.com/Document.aspx?DocID=JP4FIHBESMTMZ74.