Trilobites, change of genera and species of.

Trimen, on painting butterflies.

Trimorphism, in plants.

Trinidad, Catasetum of.
-Cruger on caprification in.

Triphaena (Triphoea) pronuba, robin attracted by colour of.

Tristan d'Acunha, Carmichael on.
-vegetation of.

Triticum repens var. littorum, bloom-experiments on.

Trollope, A., quotation by Darwin from.

Tropaeolum, Darwin's experiments on.
-peloric variety of.
-waxy secretion on leaves.

Tropical climate, in relation to colouring of insects.

Tropical plants, possible existence during cooler period.
-retreat of.

Tropics, climatic changes in.
-description of forests in.
-similarity of orders in.

Tubocytisus, Kerner on.

Tuckwell, on the Oxford British Association meeting (1860).

Tucotuco.

Tuke, D.H., on influence of mind on body.
-letter to.

Tulips.

Turkey, colour of wings, and courtship.
-muscles of tail of.

Turner, Sir W., Darwin receives assistance from.
-on Darwin's methods of correspondence.
-letters to.

Turratella.

Turtles, conversion into land-tortoises.

Tussilago, Darwin on seeds of groundsel and.

Twins, Galton's article on.

Tylor, article in "Journal of the Royal Institution" by.
-on "Early History of Mankind."

Tyndall, lack of caution.
-lecture by.
-on the Alps.
-review in the "Athenaeum" of.
-on valleys due to glaciers.
-work of.
-dogmatism of.
-on glaciers.
-on Sorby's work on cleavage.
-mentioned.

Typhlops.

Typical forms, difficult to select.
-vagueness of phrase.

Typotherium, Falconer on.

Tyrol, Mojsisovics on the Dolomites of the.

Umbelliferae, morphological characters of.
-difference in seeds from the same flower.

Undulation of light, comparison between Darwin's views and the theory
of.

Ungulates, development in N. America during Tertiary period.

United States, flora of.
-spread of Darwin's views in.

Unity of coloration, Walsh on.

Uredo, on Haematoxylon.

Ursus arctos, Lamont on.
-U. maritimus, Lamont on.

Urticaceae.

Uruguay.

D'Urville, on Canary Islands.

Use and disuse.
-in plants.

Uses, Natural Selection and.

Uspallata.

Utilitarianism, Darwin on.

Utility and inheritance.

Utopian "Flora," Darwin's idea of.

Utricularia, Darwin's work on.
-U. stellaris, Sir E. Tennent on.

Vaginulus, Darwin finds new species of.

Valeriana, two forms of.

Valleys, acti