Darwin and Modern Science

Of these products, A, B, and C constitute that part of the active deposit of the emanation which suffers rapid decay and nearly disappears in a few hours. Radium-D, continually producing its short-lived descendants E and F, remains for years on surfaces once exposed to the emanation, and makes delicate radio-active researches impossible in laboratories which have been contaminated by an escape of radium emanation.

A somewhat similar pedigree has been made out in the case of thorium. Here thorium-X is interposed between thorium and its short-lived emanation, which decays to half its initial quantity in 54 seconds. Two active deposits, thorium A and B, arise successively from the emanation. In uranium, we have the one obvious derivative uranium-X, and the question remains whether this one descent can be connected with any other individual or family. Uranium is long-lived, and emits only alpha-rays. Uranium-X decays to half value in 22 days, giving out beta- and gamma-rays. Since our evidence goes to show that radio-activity is generally accompanied by the production of new elements, it is natural to search for the substance of uranium-X in other forms, and perhaps under other names, rather than to surrender immediately our belief in the conservation of matter.

With this idea in mind we see at once the significance of the constitution of uranium minerals. Formed in the remote antiquity of past geological ages, these minerals must become store-houses of all the products of uranium except those which may have escaped as gases or possibly liquids. Even gases may be expected to some extent to be retained by occlusion. Among the contents of uranium minerals, then, we may look for the descendants of the parent uranium. If the descendants are permanent or more long-lived than uranium, they will accumulate continually. If they are short-lived, they will accumulate at a steady rate till enough is formed for the quantity disintegrating to be equal to the quantity developed. A state of mobile equilibrium will then be reached, and the amount of the product will remain constant. This constant amount of substance will depend only on the amount of uranium which is its source, and, for different minerals, if all the product is retained, the quantity of the product will be proportional to the quantity of uranium. In a series of analyses of uranium minerals, therefore, we ought to be able to pick out its more short-lived descendants by seeking for instances of such proportionality.

Now radium itself is a constituent of uranium minerals, and two series of experiments by R.J. Strutt and B.B. Boltwood have shown that the content of radium, as measured by the radio-activity of the emanation, is directly proportional to the content of uranium. (Strutt, "Proc. Roy. Soc." A, February 1905; Boltwood, "Phil. Mag." April, 1905.) In Boltwood's investigation, some twenty minerals, with amounts of uranium varying from that in a specimen of uraninite with 74.65 per cent., to that in a monazite with 0.30 per cent., gave a ratio of uranium to radium, constant within about one part in ten.

The conclusion is irresistible that radium is a descendant of uranium, though whether uranium is its parent or a more remote ancestor requires further investigation by the radio-active genealogist. On the hypothesis of direct parentage, it is easy to calculate that the amount of radium produced in a month by a kilogramme of a uranium salt would be enough to be detected easily by the radio-activity of its emanation. The investigation has been attempted by several observers, and the results, especially those of a careful experiment of Boltwood, show that from purified uranium salts the growth of radium, if appreciable at all, is much less than would be found if the radium was the first product of change of the uranium. It is necessary, therefore, to look for one or more intermediate substances.

While working in 1899 with the uranium residues used by M. and Mme Curie for the preparation of radium, Debierne discovered and partially separated another radio-active element which he called actinium. It gives rise to an intermediate product actinium-X, which yields an emanation with the short half-life of 3.9 seconds. The emanation deposits two successive disintegration products actinium-A and actinium-B.

Evidence gradually accumulated that the amounts of actinium in radio-active minerals were, roughly at any rate, proportional to the amounts of uranium. This result pointed to a lineal connection between them, and led Boltwood to undertake a direct attack on the problem. Separating a quantity of actinium from a kilogramme of ore, Boltwood observed a growth of 8.5 x (10 to the power -9) gramme of radium in 193 days, agreeing with that indicated by theory within the limits of experimental error. ("American Journal of Science", December, 1906.) We may therefore insert provisionally actinium and its series of derivatives between uranium and radium in the radio-active pedigree.

Turning to the other end of the radium series we are led to ask what becomes of radium-F when in turn it disintegrates? What is the final non-active product of the series of changes we have traced from uranium through actinium and radium?

One such product has been indicated above. The alpha-ray particles appear to possess the mass of helium atoms, and the growth of helium has been detected by its spectrum in a tube of radium emanation. Moreover, helium is found occluded in most if not all radio-active minerals in amount which approaches, but never exceeds, the quantity suggested by theory. We may safely regard such helium as formed by the accumulation of alpha-ray particles given out by successive radio-active changes.

In considering the nature of the residue left after the expulsion of the five alpha-particles, and the consequent passage of radium to radium-F we are faced by the fact that lead is a general constituent of uranium minerals. Five alpha-particles, each of atomic weight 4, taken from the atomic weight (about 225) of radium gives 205—a number agreeing fairly well with the 207 of lead. Since lead is more permanent than uranium, it must steadily accumulate, no radio-active equilibrium will be reached, and the amount of lead will depend on the age of the mineral as well as on the quantity of uranium present in it. In primary minerals from the same locality, Boltwood has shown that the contents of lead are proportional to the amounts of uranium, while, accepting this theory, the age of minerals with a given content of uranium may be calculated from the amount of lead they contain. The results vary from 400 to 2000 million years. ("American Journal of Science", October, 1905, and February, 1907.)

We can now exhibit in tabular form the amazing pedigree of radio-active change shown by this one family of elements. An immediate descent is indicated by >, while one which may either be immediate or involve an intermediate step is shown by.... No place is found in this pedigree for thorium and its derivatives. They seem to form a separate and independent radio-active family.

As soon as the transmutation theory of radio-activity was accepted, it became natural to speculate about the intimate structure of the radio-active atoms, and the mode in which they broke up with the liberation of some of their store of internal energy. How could we imagine an atomic structure which would persist unchanged for long periods of time, and yet eventually spontaneously explode, as here an atom and there an atom reached a condition of instability?

The atomic theory of corpuscles or electrons fortunately was ready to be applied to this new problem. Of the resulting speculations the most detailed and suggestive is that of J.J. Thomson. ("Phil. Mag." March, 1904.) Thomson regards the atom as composed of a number of mutually repelling negative corpuscles or electrons held together by some central attractive force which he represents by supposing them immersed in a uniform sphere of positive electricity. Under the action of the two forces, the electrons space themselves in symmetrical patterns, which depend on the number of electrons. Three place themselves at the corner of an equilateral triangle, four at those of a square, and five form a pentagon. With six, however, the single ring becomes unstable, one corpuscle moves to the middle and five lie round it. But if we imagine the system rapidly to rotate, the centrifugal force would enable the six corpuscles to remain in a single ring. Thus internal kinetic energy would maintain a configuration which would become unstable as the energy drained away. Now in a system of electrons, electromagnetic radiation would result in a loss of energy, and at one point of instability we might well have a sudden spontaneous redistribution of the constituents, taking place with an explosive violence, and accompanied by the ejection of a corpuscle as a beta-ray, or of a large fragment of the atom as an alpha-ray.

The discovery of the new property of radio-activity in a small number of chemical elements led physicists to ask whether the property might not be found in other elements, though in a much less striking form. Are ordinary materials slightly radio-active? Does the feeble electric conductivity always observed in the air contained within the walls of an electroscope depend on ionizing radiations from the material of the walls themselves? The question is very difficult, owing to the wide distribution of slight traces of radium. Contact with radium emanation results in a deposit of the fatal radium-D, which in 40 years is but half removed. Is the "natural" leak of a brass electroscope due to an intrinsic radio-activity of brass, or to traces of a radio-active impurity on its surface? Long and laborious researches have succeeded in establishing the existence of slight intrinsic radio-activity in a few metals such as potassium, and have left the wider problem still unsolved.

It should be noted, however, that, even if ordinary elements are not radio-active, they may still be undergoing spontaneous disintegration. The detection of ray-less changes by Rutherford, when those changes are interposed between two radio-active transformations which can be followed, show that spontaneous transmutation is possible without measureable radio-activity. And, indeed, any theory of disintegration, such as Thomson's corpuscular hypothesis, would suggest that atomic rearrangements are of much more general occurrence than would be apparent to one who could observe them only by the effect of the projectiles, which, in special cases, owing to some peculiarity of atomic configuration, happened to be shot out with the enormous velocity needed to ionize the surrounding gas. No evidence for such ray-less changes in ordinary elements is yet known, perhaps none may ever be obtained; but the possibility should not be forgotten.

In the strict sense of the word, the process of atomic disintegration revealed to us by the new science of radio-activity can hardly be called evolution. In each case radio-active change involves the breaking up of a heavier, more complex atom into lighter and simpler fragments. Are we to regard this process as characteristic of the tendencies in accord with which the universe has reached its present state, and is passing to its unknown future? Or have we chanced upon an eddy in a backwater, opposed to the main stream of advance? In the chaos from which the present universe developed, was matter composed of large highly complex atoms, which have formed the simpler elements by radio-active or ray-less disintegration? Or did the primaeval substance consist of isolated electrons, which have slowly come together to form the elements, and yet have left here and there an anomaly such as that illustrated by the unstable family of uranium and radium, or by some such course are returning to their state of primaeval simplicity?

INDEX.

Abraxas grossulariata.

Acquired characters, transmission of.

Acraea johnstoni.

Adaptation.

Adloff.

Adlumia cirrhosa.

Agassiz, A.

Agassiz, L.

Alexander.

Allen, C.A.

Alternation of generations.

Ameghino.

Ammon, O., Works of.

Ammonites, Descent of.

Amphidesmus analis.

Anaea divina.

Andrews, C.W.

Angiosperms, evolution of.

Anglicus, Bartholomaeus.

Ankyroderma.

Anomma.

Antedon rosacea.

Antennularia antennina.

Anthropops.

Ants, modifications of.

Arber, E.A.N.,—and J. Parkin, on the origin of Angiosperms.

Archaeopteryx.

Arctic regions, velocity of development of life in.

Ardigo.

Argelander.

Argyll, Huxley and the Duke of.

Aristotle.

Arrhenius.

Asterias, Loeb on hybridisation of.

Autogamy.

Avena fatua.

Avenarius.

Bacon, on mutability of species.

Baehr, von, on Cytology.

Baer, law of von.

Bain.

Baldwin, J.M.

Balfour, A.J.

Ball, J.

Barber, Mrs M.E., on Papilio nireus.

Barclay, W.

Barratt.

Bary, de.

Bates, H.W., on Mimicry.—Letters from Darwin to.—elsewhere.

Bateson, A.

BATESON, W., on "Heredity and Variation in Modern lights".—on discontinuous evolution.—on hybridisation.

Bateson, W. and R.P. Gregory.

Bathmism.

Beche, de la.

Beck, P.

Becquerel, H.

Beebe, C.W., on the plumage of birds.—on sexual selection.

Beguyer de Chancourtois.

Bell's (Sir Charles) "Anatomy of Expression".

Belopolsky.

Belt, T., on Mimicry.

Beneden, E. van.

Benson, M.

Bentham, G., on Darwin's species-theory.—on geographical distribution.

Bentham, Jeremy.

Bergson, H.

Berkeley.

Berthelot.

Betham, Sir W.

Bickford, E., experiments on degeneration by.

Bignonia capreolata.

Biophores.

Birds, geological history of.

Blanford, W.T.

Blaringhem, on wounding.

Blumenbach.

Bodin.

Boltwood, B.B.

Bonald, on war.

Bonnet.

Bonney, T.G.

Bonnier, G.

Bopp, F., on language.

BOUGLE C., on "Darwinism and Sociology".

Bourdeau.

Bourget, P.

Boutroux.

Boveri, T.

Brachiopods, history of.

Brassica, hybrids of.

Brassica Napus.

Broca.

Brock, on Kant.

Brown, Robert.

Brugmann and Osthoff.

Brugmann.

Brunetiere.

Bruno, on Evolution.

Buch, von.

Bucher, K.

Buckland.

Buckle.

Buffon.

Burchell, W.J.

Burck, W.

Burdon-Sanderson, J., letter from.

BURY, J.B., on "Darwinism and History".

Butler, A.G.

Butler, Samuel.

Butschli, O.

Butterflies, mimicry in.—sexual characters in.

Cabanis.

Campbell.

Camels, geological history of.

Camerarius, R.J.

Candolle, A. de.

Cannon and Davenport, experiments on Daphniae by.

Capsella bursapastoris.

Carneri.

Castnia linus.

Catasetum barbatum.

Catasetum tridentatum.

Caterpillars, variation in.

Celosia, variability of.

Cereals, variability in.

Cesnola, experiments on Mantis by.

Chaerocampa, colouring of.

Chambers, R., "The Vestiges of Creation" by.

Chromosomes and Chromomeres.

Chun.

Cieslar, experiments by.

Circumnutation, Darwin on.

Claus.

Cleistogamy.

Clerke, Miss A.

Clodd, E.

Cluer.

Clytus arietis.

Coadaptation.

Codrington.

Cohen and Peter.

Collingwood.

Colobopsis truncata.

Colour, E.B. Poulton on The Value in the Struggle for life of.—influence and temperature on changes in.—in relation to Sexual Selection.

Colours, incidental.—warning.

Comte, A.

Condorcet.

Cope.

Coral reefs, Darwin's work on.

Correlation of organisms, Darwin's idea of the.

Correlation of parts.

Corydalis claviculata.

Cournot.

Couteur, Col. Le.

Crooks, Sir William.

Cruger, on Orchids.

Cunningham and Marchand, on the brain.

Curie, M. and Mme.

Cuvier.

Cycadeoidea dacotensis.

Cycads, geological history of.

Cystidea, an ancient group.

Cytology and heredity.

Cytolysis and fertilisation.

Czapek.

Dalton's atomic theory.

Dana, J.D., on marine faunas.

Danaida chrysippus.

Danaida genutia.

Danaida plexippus.

Dante.

Dantec, Le,

Darwin, Charles, as an Anthropologist.—on ants.—and the "Beagle" Voyage.—on the Biology of Flowers.—as a Botanist.—his influence on Botany.—and S. Butler.—at Cambridge.—on Cirripedia.—on climbing plants.—on colour.—on coral reefs.—on the Descent of Man.—his work on Drosera.—at Edinburgh.—his influence on Animal Embryology.—on Geographical Distribution.—his work on Earthworms.—evolutionist authors referred to in the "Origin" by.—and E. Forbes.—on the geological record.—and Geology.—his early love for geology.—his connection with the Geological Society of London.—and Haeckel.—and Henslow.—and History.—and Hooker.—and Huxley.—on ice-action.—on igneous rocks.—on Lamarck.—on Language.—his Scientific Library.—and the Linnean Society.—and Lyell.—and Malthus.—on Patrick Matthew.—on mental evolution.—on Mimicry.—a "Monistic Philosopher."—on the movements of plants.—on Natural Selection.—a "Naturalist for Naturalists."—on Paley.

Darwin, Charles, his Pangenesis hypothesis.—on the permanence of continents.—his personality.—his influence on Philosophy.—predecessors of.—his views on religion, etc.—his influence on religious thought.—his influence on the study of religions.—his methods of research.—and Sedgwick.—on Sexual Selection.—the first germ of his species theory.—on H. Spencer.—causes of his success.—on Variation.—on the "Vestiges of Creation".—on volcanic islands.—and Wallace.—letter to Wallace from.—letter to E.B. Wilson from.

Darwin, E., on the colour of animals.—Charles Darwin's reference to.—on evolution.

DARWIN, F., on "Darwin's work on the Movements of Plants".—on Darwin as a botanist.—observations on Earthworms by.—on Lamarckism.—on Memory.—on Prichard's "Anticipations".—various.

DARWIN, SIR G., on "The Genesis of Double Stars".—on the earth's mass.

Darwin, H.

Darwin, W.

Darwinism, Sociology, Evolution and.

Davenport and Cannon, experiments on Daphniae by.

David, T.E., his work on Funafuti.

Death, cause of natural.

Debey, on Cretaceous plants.

Debierne.

Degeneration.

Delage, experiments on parthenogenesis by.

Delbruck.

Democritus.

Deniker.

Descartes.

Descent, history of doctrine of.

"Descent of Man", G. Schwalbe on "The".—Darwin on Sexual Selection in "The".—rejection in Germany of "The".

Desmatippus.

Desmoulins, A., on Geographical Distribution.

Detto.

Development, effect of environment on.

Dianthus caryophyllus.

Diderot.

Digitalis purpurea.

Dimorphism, seasonal.

Dismorphia astynome.

Dismorphia orise.

Distribution, H. Gadow on Geographical.—Sir W. Thiselton-Dyer on.

Dittrick, O.

Dixey, F.A., on the scent of Butterflies.

Dolichonyx oryzivorus.

Dorfmeister.

Down, Darwin at.

Draba verna.

Dragomirov.

Driesch, experiments by.—elsewhere.

Drosera, Darwin's work on.

Dryopithecus.

Dubois, E., on Pithecanthropus.

Duhring.

Duhamel.

Duncan, J.S.

Duncan, P.B.

Duns Scotus.

Duret, C.

Durkheim, on division of labour.

Dutrochet.

Echinoderms, ancestry of.

Ecology.

Eimer.

Ekstam.

Elephants, geological history of.

Elymnias phegea.

E. undularis.

Embleton, A.L.

Embryology, A. Sedgwick on the influence of Darwin on.

Embryology, as a clue to Phylogeny.—the Origin of Species and.

Empedocles.

Engles.

Environment, action of.—Klebs on the influence on plants of.—Loeb on experimental study in relation to.

Eohippus.

Epicurus, a poet of Evolution.

Eristalis.

Ernst.

Ernst, A., on the Flora of Krakatau.

Eschscholzia californica.

Espinas.

Eudendrium racemosum.

Evolution, in relation to Astronomy.—and creation.—conception of.—discontinuous.—experimental.—factors of.—fossil plants as evidence of.—and language.—of matter, W.C.D. Whetham on.—mental.—Lloyd Morgan on mental factors in.—Darwinism and Social.—Saltatory.—Herbert Spencer on.—Uniformitarian.—Philosophers and modern methods of studying.

Expression of the Emotions.

Fabricius, J.C., on geographical distribution.

Farmer, J.B.

Farrer, Lord.

Fearnsides, W.G.

Felton, S., on protective resemblance.

Ferri.

Ferrier, his work on the brain.

Fertilisation, experimental work on animal-.

Fertilisation of Flowers.

Fichte.

Field, Admiral A.M.

Fischer, experiments on Butterflies by.

Fitting.

Flemming, W.

Flourens.

Flowering plants, ancestry of.

Flowers, K. Goebel on the Biology of.

Flowers and Insects.

Flowers, relation of external influences to the production of.

Fol, H.

Forbes, E.—and C. Darwin.

Ford, S.O. and A.C. Seward, on the Araucarieae.

Fossil Animals, W.B. Scott on their bearing on evolution.

Fossil Plants, D.H. Scott on their bearing on evolution.

Fouillee.

Fraipont, on skulls from Spy.

FRAZER, J.G., on "Some Primitive Theories of the Origin of Man".—various.

Fruwirth.

Fumaria officinalis.

Funafuti, coral atoll of.

Fundulus.

F. heteroclitus.

GADOW, H., on "Geographical Distribution of Animals".—elsewhere.

Gartner, K.F.

Gallus bankiva.

Galton, F.

Gamble, F.W. and F.W. Keeble.

Gasca, La.

Geddes, P.

Geddes, P. and A.W. Thomson.

Gegenbauer.

Geikie, Sir A.

Geitonogamy.

Genetics.

Geographical Distribution of Animals.—of Plants.—influence of "The Origin of Species" on.—Wallace's contribution to.

Geography of former periods, reconstruction of.

Geology, Darwin and.

Geranium spinosum.

Germ-plasm, continuity of.—Weismann on.

Germinal Selection.

Gibbon.

Gilbert.

GILES, P., on "Evolution and the Science of Language".

Giuffrida-Ruggeri.

Giotto.

Gizycki.

Glossopteris Flora.

Gmelin.

Godlewski, on hybridisation.

GOEBEL, K., on "The Biology of Flowers".—his work on Morphology.

Goethe and Evolution.—on the relation between Man and Mammals.—elsewhere.

Goldfarb.

Gondwana Land.

Goodricke, J.

Gore, Dr.

Gorjanovic-Kramberger.

Gosse, P.H.

Grabau, A.W., on Fusus.

Grand'Eury, F.C., on fossil plants.

Grapta C. album.

Gravitation, effect on life-phenomena of.

Gray, Asa.

Gregoire, V.

Groom, T.T., on heliotropism.

Groos.

Grunbaum, on the brain.

Guignard, L.

Gulick.

Guppy, on plant-distribution.

Guyau.

Gwynne-Vaughan, D.T., on Osmundaceae.

Gymnadenia conopsea.

Haberlandt, G.

Haddon, A.C.

HAECKEL, E., on "Charles Darwin as an Anthropologist".—on Colour.—and Darwin.—on the Descent of Man.—contributions to Evolution by.

Haeckel, E., on Lamarck.—on Language.—a leader in the Darwinian controversy.—on Lyell's influence on Darwin.—various.

Hacker.

Hagedoorn, on hybridisation.

Hales, S.

Hansen.

Harker, A.

HARRISON, J.E., on "The Influence of Darwinism on the Study of Religions".

Hartmann, von.

Harvey.

Haupt, P., on Language.

Haycraft.

Hays, W.M.

Hegel.

Heliconius narcaea.

Heliotropism in animals.

Henslow, Rev. J.S. and Darwin.

Hensen, Van.

Herbst, his experiments on sea urchins.

Heracleitus.

Herder.

Heredity and Cytology.—Haeckel on.—and Variation.—various.

Hering, E., on Memory.

Herschel, J.

Hertwig, R.

Hertwig, O.

Hertz.

Heteromorphosis.

Heterostylism.

Heuser, E.

Hewitt.

Heyse's theory of language.

Hinde, G.J., his work on Funafuti.

Hipparion.

Hippolyte cranchii.

Hirase.

History, Darwin and.

Hobbes, T.

Hobhouse.

HOFFDING, H., on "The Influence of the Conception of Evolution on Modern Philosophy".

Hofmeister, W.

Holmes, S.J., on Arthropods.

Holothurians, calcareous bodies in skin of.

Homo heidelbergensis.

Homo neandertalensis.

Homo pampaeus.

Homo primigenius.

Homunculus.

Hooker, Sir J.D., and Darwin.—on Distribution of Plants.—on Ferns.—Letter to the Editor from.

Horner, L.

Horse, Geological history of the.

Huber.

Hubert and Mauss.

Hubrecht, A.R.W.

Hugel, F. von.

Humboldt, A. von.

Humboldt, W. von.

Hume.

Hutcheson.

Hutton.

Huxley, T.H., and Darwin.—and the Duke of Argyll.—on Embryology.—on Geographical Distribution.—on Lamarck.—Letter to J.W. Judd from.—on Lyell.—on Man.—on "The Origin of Species".—on Selection.—on Teleology.—on transmission of acquired characters.—various.

Hybridisation.

Hybrids, Sterility of.

Hyracodon.

Iberis umbellata.

Ikeno.

Imperfection of the Geological Record.

Ingenhousz, on plant physiology.

Inheritance of acquired characters.

Insects and Flowers.

Instinct.

Instincts, experimental control of animal.

Ipomaea purpurea.

Irish Elk, an example of co-adaptation.

Jacobian figures.

Jacoby, "Studies in Selection" by.

James, W.

Janczewski.

Jeans, J.H.

Jennings, H.S., on Paramoecium.

Jentsch.

Jespersen, Prof., Theory of.

Johannsen, on Species.

Jones, Sir William, on Language.

Jordan.

JUDD, J.W., on "Darwin and Geology".

Kallima, protective colouring of.

Kallima inachis.

Kammerer's experiments on Salamanders.

Kant, I.

Keane, on the Primates.

Keeble, F.W. and F.W. Gamble, on Colour-change.

Keith, on Anthropoid Apes.

Kellogg, V., on heliotropism.

Kepler.

Kerguelen Island.

Kidd.

Kidston, R., on fossil plants.

Killmann, on origin of human races.

King, Sir George.

Klaatsch, on Ancestry of Man.

Klaatsch and Hauser.

KLEBS, G., on "The influence of Environment on the forms of plants".

Kniep.

Knies.

Knight, A., experiments on plants by.—on Geotropism.

Knight-Darwin law.

Knuth.

Kolliker, his views on Evolution.

Kolreuter, J.G.

Kohl.

Korschinsky.

Kowalevsky, on fossil horses.

Krakatau, Ernst on the Flora of.

Krause, E.

Kreft, Dr.

Kropotkin.

Kupelwieser, on hybridisation.

Lagopus hyperboreus.

Lamarck, his division of the Animal Kingdom.—Darwin's opinion of.—on Evolution.—on Man.—various.

Lamarckian principle.

Lamb, C.

Lamettrie.

Lamprecht.

Lanessan, J.L. de.

Lang.

Lange.

Language, Darwin on.—Evolution and the Science of.—various.

Lankester, Sir E. Ray, on degeneration.—on educability.—on the germ-plasm theory.—elsewhere.

Lapouge, Vacher de.

Larmor, J.

Lartet, M.E.

Lassalle.

Lathyrus odoratus.

Lavelaye, de.

Lawrence, W.

Lehmann.

Lehmann-Nitsche.

Leibnitz.

Lepidium Draba.

Lepidoptera, variation in.

Leskien, A., on language.

Lessing.

Leucippus.

Levi, E.

Lewes, G.H.

Lewin, Capt.

Liapounoff.

Liddon, H.P.

Light, effect on organisms of.

Limenitis archippus.—arthemis.

Linnaeus.

Livingstone, on plant-forms.

Llamas, geological history of.

Lockyer, Sir N.

Locy, W.A.

LOEB, J., on "The Experimental Study of the influence of environment on Animals.

Loew, E.

Longstaff, G.B., on the Scents of Butterflies.

Lorentz.

Lotsy, J.P.

Love, A.E.W.

Lovejoy.

Lubbock.

Lucas, K.

Lucretius, a poet of Evolution.

Lumholtz, C.

Luteva macrophthalma.

Lycorea halia.

Lyell, Sir Charles, and Darwin.—the influence of.—on geographical distribution.—on "The Origin of Species".—on the permanence of Ocean-basins.—publication of the "Principles" by.—the uniformitarian teaching of.

Lythrum salicaria.

Macacus, ear of.

MacDougal, on wounding.

Mach, E.

Macromytis flexuosa, colour-change in.

Magic and religion.

Mahoudeau.

Maillet, de.

Majewski.

Malthus, his influence on Darwin.—various.

Mammalia, history of.

Man, Descent of.—J.G. Frazer on some primitive theories of the origin of.—mental and moral qualities of animals and.—pre-Darwinian views on the Descent of.—religious views of primitive.—Tertiary flints worked by.

"Man", G. Schwalbe on Darwin's "Descent of".

Manouvrier.

Mantis religiosa, colour experiments on.

Marett, R.R.

Markwick.

Marshall, G.A.K.

Marx.

Massart.

Masters, M.

Matonia pectinata.

Matthew, P., and Natural Selection.

Maupertuis.

Maurandia semperflorens.

Mauss and Herbert.

Mauthner.

Maxwell.

Maxwell, Clerk.

Mayer, R.

Mechanitis lysimnia.

Meehan, T.

Meldola, R., Letters from Darwin to.

Melinaea ethra.

Mendel.

Mendeleeff.

Merrifield.

Merz, J.T.

Mesembryanthemum truncatum.

Mesohippus.

Mesopithecus.

Metschnikoff.

Mill, J.S.

Mimicry.—H.W. Bates on.—F. Muller on.

Mimulus luteus.

Miquel, F.W.A.

Mobius.

Mohl, H. von.

Moltke, on war.

Monachanthus viridis.

Monkeys, fossil.

Montesquieu.

Montgomery, T.H.

Monstrosoties.

Monticelli.

Moore, J.E.S.

MORGAN, C. LLOYD, on "Mental Factors in Evolution".—on Organic Selection.

Morgan, T.H.

Morse, E.S., on colour.

Morselli.

Mortillet.

Moseley.

Mottier, M.

Muller, Fritz, "Fur Darwin" by.—on Mimicry.

Muller, Fritz.

Muller, J.

Muller, Max, on language.

Murray, A., on geographical distribution.

Murray, G.

Mutability.

Mutation.

Myanthus barbatus.

Myers, G.W., on Eclipses.

Nageli.

Nathorst, A.G.

Nathusius.

Natural Selection, and adaptation.—Darwin's views on.—Darwin and Wallace on.—and design.—and educability.—Fossil plants in relation to.—and human development.—and Mimicry.—and Mutability.—various.

Naudin.

Neandertal skulls.

Nemec.

Neoclytus curvatus.

Neodarwinism.

Neumayr, M.

Newton, A.

Newton, I.

Niebuhr.

Nietzsche.

Nilsson, on cereals.

Nitsche.

Noire.

Noll.

Novicow.

Nuclear division.

Nussbaum, M.

Nuttall, G.H.F.

Occam.

Odin.

Oecology, see Ecology.

Oenothera biennis.

Oenothera gigas.

Oenothera Lamarckiana.

Oenothera muricata.

Oenothera nanella.

Oestergren, on Holothurians.

Oken, L.

Oliver, F.W., on Palaeozoic Seeds.

Ononis minutissima.

Ophyrs apifera.

Orchids, Darwin's work on the fertilisation of.

Organic Selection.

"Origin of Species", first draft of the.—geological chapter in the.

Orthogenesis.

Ortmann, A.E.

Osborn, H.F.—"From the Greeks to Darwin" by.

Osthoff and Brugmann.

Ostwald, W.

Ovibos moschatus.

Owen, Sir Richard.

Oxford, Ashmolean Museum at.

Packard, A.S.

Palaeontological Record, D.H. Scott on the.—W.B. Scott on the.

Palaeopithecus.

Paley.

Palitzch, G.

Palm.

Pangenesis.

Panmixia, Weismann's principle of.

Papilio dardanus.

Papilio meriones.

Papilio merope.

Papilio nireus.

Paramoecium, Jennings on.

Parker, G.H., on Butterflies.

Parkin, J. and E.A.N. Arber, on the origin of Angiosperms.

Parthenogenesis, artificial.

Paul, H. and Wundt.

Pearson, K.

Peckham, Dr and Mrs, on the Attidae.

Penck.

Penzig.

Peripatus, distribution of.

Peridineae.

Permanence of continents.

Perrier, E.

Perrhybris pyrrha.

Perthes, B. de.

Peter, on sea urchin's eggs.

Petunia violacea.

Pfeffer, W.

Pfitzner, W.

Pflueger.

Phillips.

Philosophy, influence of the conception of evolution on modern.

Phryniscus nigricans.

Phylogeny, embryology as a clue to.—Palaeontological evidence on.

Physiology of plants, development of.

Piccard, on Geotropism.

Pickering, spectroscopic observations by.

Piranga erythromelas.

Pisum sativum.

Pithecanthropus.

Pitheculites.

Planema epaea.

Plants, Darwin's work on the movements of.—geographical distribution of.—Palaeontological record of fossil.

Platanthera bifolia.

Plate.

Plato.

Playfair.

Pliopithecus.

Pocock, R.I.

Poincare.

Polarity, Vochting on.

Polymorphic species.—variability in cereals.

Polypodium incanum.

Porthesia chrysorrhoea.

Potonie, R.

Pouchet, G.

POULTON, E.B., on "The Value of Colour in the Struggle for Life".—experiments on Butterflies by.—on J.C. Prichard.—on Mimicry.—various.

Pratt.

Pratz, du.

Premutation.

Preuss, K. Th.

Prichard, J.C.

Primula, heterostylism in.

Primula acaulis.

Primula elatior.

Primula officinalis.

Promeces viridis.

Pronuba yuccasella.

Protective resemblance.

Protocetus.

Protohippus.

Psychology.

Pteridophytes, history of.

Pteridospermeae.

Pucheran.

Pusey.

Quatrefages, A. de.

Quetelet, statistical investigations by.

Rabl, C.

Radio-activity.

Radiolarians.

Raimannia odorata.

Ramsay, Sir W. and Soddy.

Ranke.

Rau, A.

Ray, J.

Reade, Mellard.

Recapitulation, the theory of.

Reduction.

Regeneration.

Reid, C.

Reinke.

Religion, Darwin's attitude towards.—Darwin's influence on the study of.—and Magic.

Religious thought, Darwin's influence on.

Renard, on Darwin's work on volcanic islands.

Reproduction, effect of environment on.

Reptiles, history of.

Reversion.

Rhinoceros, the history of the.

Ridley, H.N.

Riley, C.V.

Ritchie.

Ritual.

Roberts, A.

Robertson, T.B.

Robinet.

Rolfe, R.A.

Rolph.

Romanes, G.J.

Rothert.

Roux.

Rozwadowski, von.

Ruskin.

Rutherford, E.

Rutot.

Sachs, J.

St Hilaire, E.G. de.

Salamandra atra.

Salamandra maculosa.

Saltatory Evolution, (see also Mutations).

Sanders, experiments on Vanessa by.

Saporta, on the Evolution of Angiosperms.

Sargant, Ethel, on the Evolution of Angiosperms.

Savigny.

Scardafella inca.

Scent, in relation to Sexual Selection.

Scharff, R.F.

Schelling.

Schlegel.

Schleicher, A., on language.

Schleiden and Schwann, Cell-theory of.

Schmarda, L.K., on geographical distribution.

Schoetensack, on Homo heidelbergensis.

Schreiner, K.E.

Schubler, on cereals.

Schultze, O., experiments on Frogs.

Schur.

Schutt.

SCHWALBE, G., on "The Descent of Man".

Sclater, P.L., on geographical distribution.

SCOTT, D.H., on "The Palaeontological Record (Plants)".—elsewhere.

SCOTT, W.B., on "The Palaeontological Record (Animals)".

Scrope.

Scyllaea.

Sechehaye, C.A.

SEDGWICK, A., on "The Influence of Darwin on Animal Embryology".

Sedgwick, A., Darwin's Geological Expedition with.

Seeck, O.