[179] ‘Origin of Species,’ fifth edit. 1869, p. 104. I had always perceived, that rare and strongly-marked deviations of structure, deserving to be called monstrosities, could seldom be preserved through natural selection, and that the preservation of even highly-beneficial variations would depend to a certain extent on chance. I had also fully appreciated the importance of mere individual differences, and this led me to insist so strongly on the importance of that unconscious form of selection by man, which follows from the preservation of the most valued individuals of each breed, without any intention on his part to modify the characters of the breed. But until I read an able article in the ‘North British Review’ (March, 1867, p. 289, _et seq._), which has been of more use to me than any other Review, I did not see how great the chances were against the preservation of variations, whether slight or strongly pronounced, occurring only in single individuals. [180] ‘Introduct. to the Trochilidæ,’ p. 102. [181] Gould, ‘Handbook of Birds of Australia,’ vol. ii. p. 32 and 68. [182] Audubon, ‘Ornitholog. Biography,’ 1838, vol. iv. p. 389. [183] Jerdon, ‘Birds of India,’ vol. i. p. 108; and Mr. Blyth, in ‘Land and Water,’ 1868, p. 381. [184] Graba, ‘Tagebuch, Reise nach Färo,’ 1830, s. 51-54. Macgillivray, ‘Hist. British Birds,’ vol. iii. p. 745. ‘Ibis,’ vol. v. 1863, p. 469. [185] Graba, ibid. s. 54. Macgillivray, ibid. vol. v. p. 327. [186] ‘Variation of Animals and Plants under Domestication.’ vol. ii. p. 92. [187] On these points see also ‘Variation of Animals and Plants under Domestication,’ vol. i. p. 253; vol. ii. p. 73, 75. [188] See, for instance, on the irides of a Podica and Gallicrex in ‘Ibis,’ vol. ii. 1860, p. 206; and vol. v. 1863, p. 426. [189] See also Jerdon, ‘Birds of India,’ vol. i. p. 243-245. [190] ‘Zoology of the Voyage of H.M.S. Beagle,’ 1841, p. 6. [191] Bechstein, ‘Naturgeschichte Deutschlands,’ B. iv. 1795, s. 31, on a sub-variety of the Monck pigeon. [192] This woodcut has been engraved from a beautiful drawing, most kindly made for me by Mr. Trimen; see also his description of the wonderful amount of variation in the coloration and shape of the wings of this butterfly, in his, ‘Rhopalocera Africæ Australis,’ p. 186. See also an interesting paper by the Rev. H. H. Higgins, on the origin of the ocelli in the Lepidoptera in the ‘Quarterly Journal of Science,’ July, 1868, p. 325. [193] Jerdon, ‘Birds of India,’ vol. iii. p. 517. [194] ‘Variation of Animals and Plants under Domestication,’ vol. i. p. 254.