on.
-Bates on.
-fossil.
-luminous.
-of Madeira.
-F. Muller on metamorphosis of.
-Sharp's book on.
-study of habits more valuable than description of new species.
-wingless.
-Wollaston on.
-antiquity of stridulating organs in.
-colour and Sexual Selection.
-H. Muller's work on adaptation to fertilisation of flowers.
-metamorphosis of.
-music as attraction to.
-observation on fertilisation of flowers by.
-Ramsay on.
-Riley's work on.
-tropical climate and colours of.

Instinct, Darwin and.
-in nest-making.
-selection of varying.

Insular floras.
-Hooker's lecture on.

Insular forms, in Galapagos, Canaries and Madeira.
-beaten by continental forms.

Intelligence, meaning of.
-Romanes on Animal.
-in worms.

Intercrossing, in pigeons.
-Darwin on effects of.
-and sterility.

Interglacial periods, Darwin on evidence for.

Intermediate forms.
-Bates' paper on.
-S. American types as.
-crossing and frequent absence of.
-extinction of.
-Falconer on existence of.
-as fossils.
-Asa Gray on.
-Plagiaulax as evidence of.
-Wollaston on rarity in insects.

Introduced plants, Sonchus in New Zealand as example of.
-in N. America and Australia.
-variability of.
-Darwin on.

Introductory Essay to Tasmanian "Flora," Hooker's.

Ipswich, British Association meeting (1851).

Iquique, nitrate of soda beds at.

Ireland, Spanish plants in.

Iris, flowers of.
-nectar secretion of.

Islands, comparison between species of rising and sinking.
-fauna of.
-introduction of plants.
-products of.
-plants with irregular flowers on.
-subsidence of coral.
-survival of ancient forms in.
-volcanic.
-comparison of age of continents and.
-former greater extension of.

"Island Life," Darwin's criticism of Wallace's.

Isle of Wight, occurrence of Bee-orchis in.

Isnardia palustris, range of.

Isolation, Bentham underestimates importance of.
-Darwin's opinion of.
-importance of.
-Wagner exaggerates importance of.
-Weismann on effects of.

Itajahy, F. Muller's narrow escape from flood of.

Italy, flora of.

Ivy, difference in growth of flowering and creeping branches.

Jaeger, G., letter to.
-on pangenesis and inheritance.

James', Sir H., discussion in "Athenaeum" on change of climate.
-map of the world.

James Island, Darwin's plants from.

Jameson.

Jamieson, W., on S. America.
-Darwin converted to glacial theory of