Slime of seeds.

Sloths.

Smell, Ogle's work on sense of.

Smerinthus populi-ocellatus, Weir on hybrid.

Smilaceae, reference to genera of.

Smilax, De Candolle on flower of.

Smith, Goldwin.

Smith, J., note on.

Snails of Porto Santo.

Snipe, protective colour of.

Snow, red.
-geological action of frozen.

Snowdon, elevation in recent times.

Social instincts, actions as result of.

Social plants, De Candolle on.
-in the U.S.A.

"Sociology," H. Spencer's.

Soda, nitrate beds.

Soil, in relation to plant distribution.

Solanaceae.

Solanum rostratum, Todd on stamens of.

Solenhofen, bird-creature from.

Sollas, Prof., director of the Funafuti boring expedition.
-account of the boring operations by.

Sonchus, introduced into New Zealand.

Song, importance in animal kingdom.

Sophocles, Prof., on expression of affirmation by Turks.

Sorby, on metamorphism.

Sound, and music.

Southampton, British Association meeting (1846).
-Darwin on gravel deposits at.
-Darwin's visits to.

Spanish chesnut, variation in leaf divergence.

Spanish plants in Ireland.
-in La Plata.

Spawn, dispersal of frogs'.

Spean, terraces in valley of.

Special ordination.

Specialisation.

Species, antiquity of plant-.
-belief in evolution of.
-changing into one another.
-creation of.
-Darwin recognises difficulties in and objections to his views on.
-definition of.
-descriptive work influenced by Darwin's views on.
-facts from Hooker bearing on.
-food as important factor in keeping up number of.
-frequency of.
-Asa Gray on.
-Hooker on.
-intermediate forms absent in close.
-little tendency during migration to form new.
-modification of.
-and monstrosities.
-mutability of.
-Nageli's views on.
-origin of (see Origin of Species).
-permanence of.
-Prichard on meaning of term.
-range of.
-representative.
-separate creation of.
-spreading of.
-sterility between allied.
-and sterility.
-time necessary to change.
-time of creation of new.
-variation of.
-Wallace on origin of.
-Walsh on modification of.
-Weismann on.
-Gaudry on affiliation of.
-Hackel on change of.
-isolation of.
-value of careful discrimination of.

"Species not transmutable," Bree's book on.

Specific character, Falconer on persistence of.

Speculation, Darwin on.

Spencer, H., Darwin on the advantage of his expression "survival o