ture of, in relation to crossing, 97.
---- of compositae and umbelliferae, 144.
Forbes, E., on colours of shells, 132.
---- on abrupt range of shells in depth, 175.
---- on poorness of palaeontological collections, 288.
---- on continuous succession of genera, 316.
---- on continental extensions, 357.
---- on distribution during glacial period, 366.
---- on parallelism in time and space, 409.
Forests, changes in, in America, 74.
Formation, Devonian, 334.
Formations, thickness of, in Britain, 284.
----, intermittent, 290.
Formica rufescens, 219.
---- sanguinea, 219.
---- flava, neuter of, 240.
Frena, ovigerous, of cirripedes, 192.
Fresh-water productions, dispersal of, 383.
Fries on species in large genera being closely allied to other species,
57.
Frigate-bird, 185.
Frogs on islands, 393.
Fruit-trees, gradual improvement of, 37.
---- ---- in United States, 85.
---- ----, varieties of, acclimatised in United States, 142.
{495}
Fuci, crossed, 258.
Fur, thicker in cold climates, 133.
Furze, 439.

G.

Galapagos Archipelago, birds of, 390.
----, productions of, 398, 400.
Galeopithecus, 181.
Game, increase of, checked by vermin, 68.
Gaertner on sterility of hybrids, 247, 255.
----, on reciprocal crosses, 258.
----, on crossed maize and verbascum, 270.
----, on comparison of hybrids and mongrels, 272.
Geese, fertility when crossed, 253.
----, upland, 185.
Genealogy important in classification, 425.
Geoffroy St. Hilaire on balancement, 147.
---- ---- on homologous organs, 434.
---- ----, Isidore, on variability of repeated parts, 149.
---- ----, on correlation in monstrosities, 11.
---- ----, on correlation, 144.
---- ----, on variable parts being often monstrous, 155.
Geographical distribution, 346.
Geography, ancient, 487.
Geology, future progress of, 487.
----, imperfection of the record, 279.
Giraffe, tail of, 195.
Glacial period, 365.
Gmelin on distribution, 365.
Gnathodon, fossil, 368.
Godwin-Austen, Mr., on the Malay Archipelago, 300.
Goethe on compensation of growth, 147.
Gooseberry, grafts of, 262.
Gould, Dr. A., on land-shells, 397.
----, Mr., on colours of birds, 132.
----, on birds of the Galapagos, 398.
----, on distribution of genera of birds, 404.
Gourds, crossed, 270.
Grafts, capacity of, 261.
Grasses, varieties of, 113.
Gray, Dr. Asa, on tree