Chapter I: the Observer

Journal des Goncourts, May 1, 1857, vol. I, p. 182.

Ben Jonson, The Poetaster, act II, scene 1.

Sentimental Journey, ‘In the Street.’

Portraits Littéraires, vol. III, p. 546.

Expression, p. 80.

Thoreau, Journal, vol. VII, p. 46.

Gray, to Darwin, May 18, 1862, Gray, Letters, vol. II, p. 481.

Great Naturalists, p. 51.

More Letters, vol. I, p. 72.

Life, vol. I, p. 83.

To Farrar, November 26, 1868, Life, vol. II, p. 453.

To Hooker, 1867, More Letters, vol. II, p. 6.

To Lyell, June 1, 1867, Life, vol. II, p. 248.

To Wilson, April 29, 1878, More Letters, vol. II, p. 421.

To Galton, November, 1879, Life, vol. II, p. 414.

To Lyell, March 17, 1863, Life, vol. II, p. 201.

To Galton, November 8, 1872, More Letters, vol. II, p. 108.

Expression, p. 184.

To Dr. Ogle, March 12, 1871, Life, vol. II, p. 321.

More Letters, vol. I, p. 4.

To Jenyns, October 17, 1846, Life, vol. I, p. 396.

Beagle Journal, p. 282.

To Gray, June 3, 1874, Life, vol. II, p. 457.

To Hooker, December 11, 1860, Life, vol. II, p. 148.

To Scott, July 2, 1863, More Letters, vol. II, p. 323.

To Horner, January, 1847, More Letters, vol. II, p. 224.

Expression, p. 12.

Life, vol. II, p. 238.

More Letters, vol. II, p. 105.

Life, vol. I, p. 40.

Different Forms of Flowers, p. 189.

To Wiesner, October 4, 1881, More Letters, vol. II, p. 432.

Life, vol. I, p. 124.

Ibid.

Life, vol. I, p. 125.

Life, vol. II, p. 453.

Cirripedia, p. 155.

To Lyell, September 12, 1860, Life, vol. II, p. 133.

Darwiniana, p. 275.

To Hooker, February 4, 1861, Life, vol. II, p. 153.

To Lyell, March 9, 1850, More Letters, vol. II, p. 229.

Life, vol. I, p. 125.

Life, vol. I, p. 105.

Life, vol. I, p. 80.

Life, vol. I, p. 121.

Purgatorio, canto III.

To Miss S. Darwin, August 4, 1836, Life, vol. I, p. 237.

To Hooker, 1847, Life, vol. I, p. 317.

More Letters, vol. I, p. 3.

To Miss C. Darwin, November 8, 1834, Life, vol. I, p. 230.

Beagle Journal, p. 78.

Life, vol. I, p. 109.

Expression, p. 194.

To Romanes, May 29, 1876, More Letters, vol. I, p. 364.

To Fox, May, 1832, Life, vol. I, p. 206.

To Henslow, May 18, 1832, Life, vol. I, p. 208.

To Henslow, August 15, 1832, More Letters, vol. I, p. 9.

Journal, August 29, 1858, vol. XI, p. 137.

Journal, December 4, 1856, vol. IX, p. 158.

Life, vol. I, p. 368.

Worms, p. 97.

Origin, p. 105.

In Popular Science Monthly, April, 1909, vol. LXXIV, p. 198.