Humble-bees, cells of, 225.

Hunter, J., on secondary sexual characters, 150.

Hutton, Captain, on crossed geese, 253.

Huxley, Professor:  on structure of hermaphrodites, 101. on embryological succession, 338. on homologous organs, 438. on the development of aphis, 442.

Hybrids and mongrels compared, 272.

Hybridism, 245.

Hydra, structure of, 190.

Ibla, 148.

Icebergs transporting seeds, 363.

Increase, rate of, 63.

Individuals:  numbers favourable to selection, 102. many, whether simultaneously created, 356.

Inheritance:  laws of, 12. at corresponding ages, 14, 86.

Insects:  colour of, fitted for habitations, 84. sea-side, colours of, 132. blind, in caves, 138. luminous, 193. neuter, 236.

Instinct, 207.

Instincts, domestic, 213.

Intercrossing, advantages of, 96.

Islands, oceanic, 388.

Isolation favourable to selection, 104.

Japan, productions of, 372.

Java, plants of, 375.

Jones, Mr. J. M., on the birds of Bermuda, 391.

Jussieu on classification, 417.

Kentucky, caves of, 137.

Kerguelen-land, flora of, 381, 399.

Kidney-bean, acclimatisation of, 142.

Kidneys of birds, 144.

Kirby on tarsi deficient in beetles, 135.

Knight, Andrew, on cause of variation, 7.

Kolreuter:  on the barberry, 98. on sterility of hybrids, 247. on reciprocal crosses, 258. on crossed varieties of nicotiana, 271. on crossing male and hermaphrodite flowers, 451.

Lamarck on adaptive characters, 427.

Land-shells:  distribution of, 397. of Madeira, naturalised, 402.

Languages, classification of, 422.

Lapse, great, of time, 282.

Larvae, 440.

Laurel, nectar secreted by the leaves, 92.

Laws of variation, 131.

Leech, varieties of, 76.

Leguminosae, nectar secreted by glands, 92.

Lepidosiren, 107, 330.

Life, struggle for, 60.

Lingula, Silurian, 306.

Linnaeus, aphorism of, 413.

Lion:  mane of, 88. young of, striped, 439.

Lobelia fulgens, 73, 98,

Lobelia, sterility of crosses, 250.

Loess of the Rhine, 384.

Lowness of structure connected with variability, 149.

Lowness, related to wide distribution, 406.

Lubbock, Mr., on the nerves of coccus, 46.

Lucas, Dr. P.:  on inheritance, 12. on resemblance of child to parent, 275.

Lund and Clausen on fossils of Brazil, 339.

Lyell, Sir C.:  on the struggle for existence, 62. on modern changes of the earth, 95. on measure of denudation, 283. on a carboniferous land-shell, 289. on fossil whales, 303. on strata beneath Silurian system, 307. on the imperfection of the geological record, 310. on the appearance of species, 312. on Barrande’s colonies, 313. on tertiary formations of Europe and North America, 323. on parallelism of tertiary formations, 328. on transport of seeds by icebergs, 363. on great alternations of climate, 382. on the distribution of fresh-water shells, 385. on land-shells of Madeira, 402.