INDEX

LIST OF ILLUSTRATIONS

Porto Praya — Ribeira Grande — Atmospheric Dust with Infusoria — Habits of a Sea-slug and Cuttle-fish — St. Paul's Rocks, non-volcanic — Singular Incrustations — Insects the first Colonists of Islands — Fernando Noronha — Bahia — Burnished Rocks — Habits of a Diodon — Pelagic Confervæ and Infusoria — Causes of discoloured Sea.

Rio de Janeiro — Excursion north of Cape Frio — Great Evaporation — Slavery — Botofogo Bay — Terrestrial Planariae — Clouds on the Corcovado — Heavy Rain — Musical Frogs — Phosphorescent insects — Elater, springing powers of — Blue Haze — Noise made by a Butterfly — Entomology — Ants — Wasp killing a Spider — Parasitical Spider — Artifices of an Epeira — Gregarious Spider — Spider with an unsymmetrical web.

Monte Video — Maldonado — Excursion to R. Polanco — Lazo and Bolas — Partridges — Absence of trees — Deer — Capybara, or River Hog — Tucutuco — Molothrus, cuckoo-like habits — Tyrant-flycatcher — Mocking-bird — Carrion Hawks — Tubes formed by lightning — House struck.

Rio Negro — Estancias attacked by the Indians — Salt-Lakes — Flamingoes — R. Negro to R. Colorado — Sacred Tree — Patagonian Hare — Indian Families — General Rosas — Proceed to Bahia Blanca — Sand Dunes — Negro Lieutenant — Bahia Blanca — Saline incrustations — Punta Alta — Zorillo.

Bahia Blanca — Geology — Numerous gigantic extinct Quadrupeds — Recent Extinction — Longevity of Species — Large Animals do not require a luxuriant vegetation — Southern Africa — Siberian Fossils — Two Species of Ostrich — Habits of Oven-bird — Armadilloes — Venomous Snake, Toad, Lizard — Hybernation of Animals — Habits of Sea-Pen — Indian Wars and Massacres — Arrowhead — Antiquarian Relic.

Set out for Buenos Ayres — Rio Sauce — Sierra Ventana — Third Posta — Driving Horses — Bolas — Partridges and Foxes — Features of the country — Long-legged Plover — Teru-tero — Hail-storm — Natural enclosures in the Sierra Tapalguen — Flesh of Puma — Meat Diet — Guardia del Monte — Effects of cattle on the Vegetation — Cardoon — Buenos Ayres — Corral where cattle are slaughtered.

Excursion to St. Fé — Thistle Beds — Habits of the Bizcacha — Little Owl — Saline streams — Level plains — Mastodon — St. Fé — Change in landscape — Geology — Tooth of extinct Horse — Relation of the Fossil and recent Quadrupeds of North and South America — Effects of a great drought — Parana — Habits of the Jaguar — Scissor-beak — Kingfisher, Parrot, and Scissor-tail — Revolution — Buenos Ayres — State of Government.

Excursion to Colonia del Sacramiento — Value of an Estancia — Cattle, how counted — Singular breed of Oxen — Perforated pebbles — Shepherd-dogs — Horses broken-in, Gauchos riding — Character of Inhabitants — Rio Plata — Flocks of Butterflies — Aeronaut Spiders — Phosphorescence of the Sea — Port Desire — Guanaco — Port St. Julian — Geology of Patagonia — Fossil gigantic Animal — Types of Organisation constant — Change in the Zoology of America — Causes of Extinction.

Santa Cruz — Expedition up the River — Indians — Immense streams of basaltic lava — Fragments not transported by the river — Excavation of the valley — Condor, habits of — Cordillera — Erratic boulders of great size — Indian relics — Return to the ship — Falkland Islands — Wild horses, cattle, rabbits — Wolf-like fox — Fire made of bones — Manner of hunting wild cattle — Geology — Streams of stones — Scenes of violence — Penguin — Geese — Eggs of Doris — Compound animals.

Tierra del Fuego, first arrival — Good Success Bay — An account of the Fuegians on board — Interview with the savages — Scenery of the forests — Cape Horn — Wigwam Cove — Miserable condition of the savages — Famines — Cannibals — Matricide — Religious feelings — Great Gale — Beagle Channel — Ponsonby Sound — Build wigwams and settle the Fuegians — Bifurcation of the Beagle Channel — Glaciers — Return to the Ship — Second visit in the Ship to the Settlement — Equality of condition amongst the natives.

Strait of Magellan — Port Famine — Ascent of Mount Tarn — Forests — Edible fungus — Zoology — Great Seaweed — Leave Tierra del Fuego — Climate — Fruit-trees and productions of the southern coasts — Height of snow-line on the Cordillera — Descent of glaciers to the sea — Icebergs formed — Transportal of boulders — Climate and productions of the Antarctic Islands — Preservation of frozen carcasses — Recapitulation.

Valparaiso — Excursion to the foot of the Andes — Structure of the land — Ascend the Bell of Quillota — Shattered masses of greenstone — Immense valleys — Mines — State of miners — Santiago — Hot-baths of Cauquenes — Gold-mines — Grinding-mills — Perforated stones — Habits of the Puma — El Turco and Tapacolo — Humming-birds.

Chiloe — General aspect — Boat excursion — Native Indians — Castro — Tame fox — Ascend San Pedro — Chonos Archipelago — Peninsula of Tres Montes — Granitic range — Boat-wrecked sailors — Low's Harbour — Wild potato — Formation of peat — Myopotamus, otter and mice — Cheucau and Barking-bird — Opetiorhynchus — Singular character of ornithology — Petrels.

San Carlos, Chiloe — Osorno in eruption, contemporaneously with Aconcagua and Coseguina — Ride to Cucao — Impenetrable forests — Valdivia — Indians — Earthquake — Concepcion — Great earthquake — Rocks fissured — Appearance of the former towns — The sea black and boiling — Direction of the vibrations — Stones twisted round — Great Wave — Permanent Elevation of the land — Area of volcanic phenomena — The connection between the elevatory and eruptive forces — Cause of earthquakes — Slow elevation of mountain-chains.

Valparaiso — Portillo Pass — Sagacity of mules — Mountain-torrents — Mines, how discovered — Proofs of the gradual elevation of the Cordillera — Effect of snow on rocks — Geological structure of the two main ranges, their distinct origin and upheaval — Great subsidence — Red snow — Winds — Pinnacles of snow — Dry and clear atmosphere — Electricity — Pampas — Zoology of the opposite sides of the Andes — Locusts — Great Bugs — Mendoza — Uspallata Pass — Silicified trees buried as they grew — Incas Bridge — Badness of the passes exaggerated — Cumbre — Casuchas — Valparaiso.

Coast-road to Coquimbo — Great loads carried by the miners — Coquimbo — Earthquake — Step-formed terraces — Absence of recent deposits — Contemporaneousness of the Tertiary formations — Excursion up the valley — Road to Guasco — Deserts — Valley of Copiapó — Rain and Earthquakes — Hydrophobia — The Despoblado — Indian ruins — Probable change of climate — River-bed arched by an earthquake — Cold gales of wind — Noises from a hill — Iquique — Salt alluvium — Nitrate of soda — Lima — Unhealthy country — Ruins of Callao, overthrown by an earthquake — Recent subsidence — Elevated shells on San Lorenzo, their decomposition — Plain with embedded shells and fragments of pottery — Antiquity of the Indian Race.

Galapagos Archipelago — The whole group volcanic — Number of craters — Leafless bushes — Colony at Charles Island — James Island — Salt-lake in crater — Natural history of the group — Ornithology, curious finches — Reptiles — Great tortoises, habits of — Marine lizard, feeds on seaweed — Terrestrial lizard, burrowing habits, herbivorous — Importance of reptiles in the Archipelago — Fish, shells, insects — Botany — American type of organisation — Differences in the species or races on different islands — Tameness of the birds — Fear of man an acquired instinct.

Pass through the Low Archipelago — Tahiti — Aspect — Vegetation on the mountains — View of Eimeo — Excursion into the interior — Profound ravines — Succession of waterfalls — Number of wild useful plants — Temperance of the inhabitants — Their moral state — Parliament convened — New Zealand — Bay of Islands — Hippahs — Excursion to Waimate — Missionary establishment — English weeds now run wild — Waiomio — Funeral of a New Zealand woman — Sail for Australia.

Sydney — Excursion to Bathurst — Aspect of the woods — Party of natives — Gradual extinction of the aborigines — Infection generated by associated men in health — Blue Mountains — View of the grand gulf-like valleys — Their origin and formation — Bathurst, general civility of the lower orders — State of Society — Van Diemen's Land — Hobart Town — Aborigines all banished — Mount Wellington — King George's Sound — Cheerless aspect of the country — Bald Head, calcareous casts of branches of trees — Party of natives — Leave Australia.

Keeling Island — Singular appearance — Scanty Flora — Transport of seeds — Birds and insects — Ebbing and flowing springs — Fields of dead coral — Stones transported in the roots of trees — Great crab — Stinging corals — Coral-eating fish — Coral formations — Lagoon islands or atolls — Depth at which reef-building corals can live — Vast areas interspersed with low coral islands — Subsidence of their foundations — Barrier-reefs — Fringing-reefs — Conversion of fringing-reefs into barrier-reefs, and into atolls — Evidence of changes in level — Breaches in barrier-reefs — Maldiva atolls, their peculiar structure — Dead and submerged reefs — Areas of subsidence and elevation — Distribution of volcanoes — Subsidence slow and vast in amount.

Mauritius, beautiful appearance of — Great crateriform ring of mountains — Hindoos — St. Helena — History of the changes in the vegetation — Cause of the extinction of land-shells — Ascension — Variation in the imported rats — Volcanic bombs — Beds of infusoria — Bahia, Brazil — Splendour of tropical scenery — Pernambuco — Singular reefs — Slavery — Return to England — Retrospect on our voyage.

INDEX

LIST OF ILLUSTRATIONS

ESSAY OF 1842

• PAGES
  
• Introduction xi

PART I

• § i. On variation under domestication, and on the principles of selection 1
• § ii. On variation in a state of nature and on the natural means of selection 4
• § iii. On variation in instincts and other mental attributes 17

PART II

• §§ iv. and v. On the evidence from Geology. (The reasons for combining the two sections are given in the Introduction) 22
• § vi. Geographical distribution 29
• § vii. Affinities and classification 35
• § viii. Unity of type in the great classes 38
• § ix. Abortive organs 45
• § x. Recapitulation and conclusion 48

{viii}

ESSAY OF 1844

PART I

CHAPTER I
ON THE VARIATION OF ORGANIC BEINGS UNDER DOMESTICATION; AND ON THE PRINCIPLES OF SELECTION.

• Variation
• On the hereditary tendency
• Causes of Variation
• On Selection
• Crossing Breeds
• Whether our domestic races have descended from one or more wild stocks
• Limits to Variation in degree and kind
• In what consists Domestication
• Summary 57-80

CHAPTER II
ON THE VARIATION OF ORGANIC BEINGS IN A WILD STATE; ON THE NATURAL MEANS OF SELECTION; AND ON THE COMPARISON OF DOMESTIC RACES AND TRUE SPECIES.

• Variation
• Natural means of Selection
• Differences between “Races” and “Species”:—first, in their trueness or variability
• Difference between “Races” and “Species” in fertility when crossed
• Causes of Sterility in Hybrids
• Infertility from causes distinct from hybridisation
• Points of Resemblance between “Races” and “Species”
• External characters of Hybrids and Mongrels
• Summary
• Limits of Variation 81-111

CHAPTER III
ON THE VARIATION OF INSTINCTS AND OTHER MENTAL ATTRIBUTES UNDER DOMESTICATION AND IN A STATE OF NATURE; ON THE DIFFICULTIES IN THIS SUBJECT; AND ON ANALOGOUS DIFFICULTIES WITH RESPECT TO CORPOREAL STRUCTURES.

• Variation of mental attributes under domestication
• Hereditary habits compared with instincts
• Variation in the mental attributes of wild animals
• Principles of Selection applicable to instincts
• Difficulties in the acquirement of complex instincts by Selection
• Difficulties in the acquirement by Selection of complex corporeal structures 112-132

{ix}

PART II
ON THE EVIDENCE FAVOURABLE AND OPPOSED TO THE VIEW THAT SPECIES ARE NATURALLY FORMED RACES, DESCENDED FROM COMMON STOCKS.

CHAPTER IV
ON THE NUMBER OF INTERMEDIATE FORMS REQUIRED ON THE THEORY OF COMMON DESCENT; AND ON THEIR ABSENCE IN A FOSSIL STATE 133-143

CHAPTER V
GRADUAL APPEARANCE AND DISAPPEARANCE OF SPECIES. 144-150

• Gradual appearance of species
• Extinction of species

CHAPTER VI
ON THE GEOGRAPHICAL DISTRIBUTION OF ORGANIC BEINGS IN PAST AND PRESENT TIMES.

SECTION FIRST 151-174

• Distribution of the inhabitants in the different continents
• Relation of range in genera and species
• Distribution of the inhabitants in the same continent
• Insular Faunas
• Alpine Floras
• Cause of the similarity in the floras of some distant mountains
• Whether the same species has been created more than once
• On the number of species, and of the classes to which they belong in different regions

SECOND SECTION 174-182

• Geographical distribution of extinct organisms
• Changes in geographical distribution
• Summary on the distribution of living and extinct organic beings

SECTION THIRD 183-197

• An attempt to explain the foregoing laws of geographical distribution, on the theory of allied species having a common descent
• Improbability of finding fossil forms intermediate between existing species

CHAPTER VII
ON THE NATURE OF THE AFFINITIES AND CLASSIFICATION
OF ORGANIC BEINGS. 198-213

• Gradual appearance and disappearance of groups
• What is the Natural System?
• On the kind of relation between distinct groups
• Classification of Races or Varieties
• Classification of Races and Species similar
• Origin of genera and families

{x}

CHAPTER VIII
UNITY OF TYPE IN THE GREAT CLASSES; AND MORPHOLOGICAL STRUCTURES.

• Unity of Type
• Morphology
• Embryology
• Attempt to explain the facts of embryology
• On the graduated complexity in each great class
• Modification by selection of the forms of immature animals
• Importance of embryology in classification
• Order in time in which the great classes have first appeared 214-230

CHAPTER IX
ABORTIVE OR RUDIMENTARY ORGANS.

• The abortive organs of Naturalists
• The abortive organs of Physiologists
• Abortion from gradual disuse 231-238

CHAPTER X
RECAPITULATION AND CONCLUSION.

• Recapitulation
• Why do we wish to reject the Theory of Common Descent?
• Conclusion 239-255
  
• Index 257
  
• Portrait frontispiece
• Facsimile to face p. 50

INTRODUCTION

Page 1

CHAPTER I.

Variation under Domestication.

Causes of Variability—Effects of Habit—Correlation of Growth—Inheritance—Character of Domestic Varieties—Difficulty of distinguishing between Varieties and Species—Origin of Domestic Varieties from one or more Species—Domestic Pigeons, their Differences and Origin—Principle of Selection anciently followed, its Effects—Methodical and Unconscious Selection—Unknown Origin of our Domestic Productions—Circumstances favourable to Man's power of Selection

7-43

CHAPTER II.

Variation under Nature.

Variability—Individual differences—Doubtful species—Wide ranging, much diffused, and common species vary most—Species of the larger genera in any country vary more than the species of the smaller genera—Many of the species of the larger genera resemble varieties in being very closely, but unequally, related to each other, and in having restricted ranges

44-59

CHAPTER III.

Struggle for Existence.

Its bearing on natural selection—The term used in a wide sense—Geometrical powers of increase—Rapid increase of naturalised animals and plants—Nature of the checks to increase—Competition universal—Effects of climate—Protection from the number of individuals—Complex relations of all animals and plants throughout nature—Struggle for life most severe between individuals and varieties of the same species; often severe between species of the same genus—The relation of organism to organism the most important of all relations

60-79

CHAPTER IV.

Natural Selection.

Natural Selection—its power compared with man's selection—its power on characters of trifling importance—its power at all ages and on both sexes—Sexual Selection—On the generality of intercrosses between individuals of the same species—Circumstances favourable and unfavourable to Natural Selection, namely, intercrossing, isolation, number of individuals—Slow action—Extinction caused by Natural Selection—Divergence of Character, related to the diversity of inhabitants of any small area, and to naturalisation—Action of Natural Selection, through Divergence of Character and Extinction, on the descendants from a common parent—Explains the Grouping of all organic beings

80-130

CHAPTER V.

Laws of Variation.

Effects of external conditions—Use and disuse, combined with natural selection; organs of flight and of vision—Acclimatisation—Correlation of growth—Compensation and economy of growth—False correlations—Multiple, rudimentary, and lowly organised structures variable—Parts developed in an unusual manner are highly variable: specific characters more variable than generic: secondary sexual characters variable—Species of the same genus vary in an analogous manner—Reversions to long-lost characters—Summary

131-170

CHAPTER VI.

Difficulties on Theory.

Difficulties on the theory of descent with modification—Transitions—Absence or rarity of transitional varieties—Transitions in habits of life—Diversified habits in the same species—Species with habits widely different from those of their allies—Organs of extreme perfection—Means of transition—Cases of difficulty—Natura non facit saltum—Organs of small importance—Organs not in all cases absolutely perfect—The law of Unity of Type and of the Conditions of Existence embraced by the theory of Natural Selection

171-206

CHAPTER VII.

Instinct.

Instincts comparable with habits, but different in their origin—Instincts graduated—Aphides and ants—Instincts variable—Domestic instincts, their origin—Natural instincts of the cuckoo, ostrich, and parasitic bees—Slave-making ants—Hive-bee, its cell-making instinct—Difficulties on the theory of the Natural Selection of instincts—Neuter or sterile insects—Summary

207-244

CHAPTER VIII.

Hybridism.

Distinction between the sterility of first crosses and of hybrids—Sterility various in degree, not universal, affected by close interbreeding, removed by domestication—Laws governing the sterility of hybrids—Sterility not a special endowment, but incidental on other differences—Causes of the sterility of first crosses and of hybrids—Parallelism between the effects of changed conditions of life and crossing—Fertility of varieties when crossed and of their mongrel offspring not universal—Hybrids and mongrels compared independently of their fertility—Summary

245-278

CHAPTER IX.

On the Imperfection of the Geological Record.

On the absence of intermediate varieties at the present day—On the nature of extinct intermediate varieties; on their number—On the vast lapse of time, as inferred from the rate of deposition and of denudation—On the poorness of our palæontological collections—On the intermittence of geological formations—On the absence of intermediate varieties in any one formation—On the sudden appearance of groups of species—On their sudden appearance in the lowest known fossiliferous strata

279-311

CHAPTER X.

On the Geological Succession of Organic Beings.

On the slow and successive appearance of new species—On their different rates of change—Species once lost do not reappear—Groups of species follow the same general rules in their appearance and disappearance as do single species—On Extinction—On simultaneous changes in the forms of life throughout the world—On the affinities of extinct species to each other and to living species—On the state of development of ancient forms—On the succession of the same types within the same areas—Summary of preceding and present chapters

312-345

CHAPTER XI.

Geographical Distribution.

Present distribution cannot be accounted for by differences in physical conditions—Importance of barriers—Affinity of the productions of the same continent—Centres of creation—Means of dispersal, by changes of climate and of the level of the land, and by occasional means—Dispersal during the Glacial period co-extensive with the world

346-382

CHAPTER XII.

Geographical Distribution—continued.

Distribution of fresh-water productions—On the inhabitants of oceanic islands—Absence of Batrachians and of terrestrial Mammals—On the relation of the inhabitants of islands to those of the nearest mainland—On colonisation from the nearest source with subsequent modification—Summary of the last and present chapters

383-410

CHAPTER XIII.

Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs.

Classification, groups subordinate to groups—Natural system—Rules and difficulties in classification, explained on the theory of descent with modification—Classification of varieties—Descent always used in classification—Analogical or adaptive characters—Affinities, general, complex and radiating—Extinction separates and defines groups—Morphology, between members of the same class, between parts of the same individual—Embryology, laws of, explained by variations not supervening at an early age, and being inherited at a corresponding age—Rudimentary organs; their origin explained—Summary

411-458

CHAPTER XIV.

Recapitulation and Conclusion.

Recapitulation of the difficulties on the theory of Natural Selection—Recapitulation of the general and special circumstances in its favour—Causes of the general belief in the immutability of species—How far the theory of natural selection may be extended—Effects of its adoption on the study of Natural history—Concluding remarks

459-490

INTRODUCTION ... Page 1

DOMESTIC DOGS AND CATS.

ANCIENT VARIETIES OF THE DOG—RESEMBLANCE OF DOMESTIC DOGS IN VARIOUS COUNTRIES TO NATIVE CANINE SPECIES—ANIMALS NOT ACQUAINTED WITH MAN AT FIRST FEARLESS—DOGS RESEMBLING WOLVES AND JACKALS—HABIT OF BARKING ACQUIRED AND LOST—FERAL DOGS—TAN-COLOURED EYE-SPOTS—PERIOD OF GESTATION—OFFENSIVE ODOUR—FERTILITY OF THE RACES WHEN CROSSED—DIFFERENCES IN THE SEVERAL RACES IN PART DUE TO DESCENT FROM DISTINCT SPECIES—DIFFERENCES IN THE SKULL AND TEETH—DIFFERENCES IN THE BODY, IN CONSTITUTION—FEW IMPORTANT DIFFERENCES HAVE BEEN FIXED BY SELECTION—DIRECT ACTION OF CLIMATE—WATER-DOGS WITH PALMATED FEET—HISTORY OF THE CHANGES WHICH CERTAIN ENGLISH RACES OF THE DOG HAVE GRADUALLY UNDERGONE THROUGH SELECTION—EXTINCTION OF THE LESS IMPROVED SUB-BREEDS.

CATS, CROSSED WITH SEVERAL SPECIES—DIFFERENT BREEDS FOUND ONLY IN SEPARATED COUNTRIES—DIRECT EFFECTS OF THE CONDITIONS OF LIFE—FERAL CATS—INDIVIDUAL VARIABILITY ... Page 15

HORSES AND ASSES.

HORSE.—DIFFERENCES IN THE BREEDS—INDIVIDUAL VARIABILITY OF—DIRECT EFFECTS OF THE CONDITIONS OF LIFE—CAN WITHSTAND MUCH COLD—BREEDS MUCH MODIFIED BY SELECTION—COLOURS OF THE HORSE—DAPPLING—DARK STRIPES ON THE SPINE, LEGS, SHOULDERS, AND FOREHEAD—DUN-COLOURED HORSES MOST FREQUENTLY STRIPED—STRIPES PROBABLY DUE TO REVERSION TO THE PRIMITIVE STATE OF THE HORSE.

ASSES.—BREEDS OF—COLOUR OF—LEG- AND SHOULDER-STRIPES—SHOULDER-STRIPES SOMETIMES ABSENT, SOMETIMES FORKED ... Page 49

PIGS—CATTLE—SHEEP—GOATS.

PIGS BELONG TO TWO DISTINCT TYPES, SUS SCROFA AND INDICA—TORF-SCHWEIN—JAPAN PIG—FERTILITY OF CROSSED PIGS—CHANGES IN THE SKULL OF THE HIGHLY CULTIVATED RACES—CONVERGENCE OF CHARACTER—GESTATION—SOLID-HOOFED SWINE—CURIOUS APPENDAGES TO THE JAWS—DECREASE IN SIZE OF THE TUSKS—YOUNG PIGS LONGITUDINALLY STRIPED—FERAL PIGS—CROSSED BREEDS.

CATTLE.—ZEBU A DISTINCT SPECIES—EUROPEAN CATTLE PROBABLY DESCENDED FROM THREE WILD FORMS—ALL THE RACES NOW FERTILE TOGETHER—BRITISH PARK CATTLE—ON THE COLOUR OF THE ABORIGINAL SPECIES—CONSTITUTIONAL DIFFERENCES—SOUTH AFRICAN RACES—SOUTH AMERICAN RACES—NIATA CATTLE—ORIGIN OF THE VARIOUS RACES OF CATTLE. {iv}

SHEEP.—REMARKABLE RACES OF—VARIATIONS ATTACHED TO THE MALE SEX—ADAPTATIONS TO VARIOUS CONDITIONS—GESTATION OF—CHANGES IN THE WOOL—SEMI-MONSTROUS BREEDS.

GOATS.—REMARKABLE VARIATIONS OF ... Page 65

DOMESTIC RABBITS.

DOMESTIC RABBITS DESCENDED FROM THE COMMON WILD RABBIT—ANCIENT DOMESTICATION—ANCIENT SELECTION—LARGE LOP-EARED RABBITS—VARIOUS BREEDS—FLUCTUATING CHARACTERS—ORIGIN OF THE HIMALAYAN BREED—CURIOUS CASE OF INHERITANCE—FERAL RABBITS IN JAMAICA AND THE FALKLAND ISLANDS—PORTO SANTO FERAL RABBITS—OSTEOLOGICAL CHARACTERS—SKULL—SKULL OF HALF-LOP RABBITS—VARIATIONS IN THE SKULL ANALOGOUS TO DIFFERENCES IN DIFFERENT SPECIES OF HARES—VERTEBRÆ—STERNUM—SCAPULA—EFFECTS OF USE AND DISUSE ON THE PROPORTIONS OF THE LIMBS AND BODY—CAPACITY OF THE SKULL AND REDUCED SIZE OF THE BRAIN—SUMMARY ON THE MODIFICATIONS OF DOMESTICATED RABBITS ... Page 103

DOMESTIC PIGEONS.

ENUMERATION AND DESCRIPTION OF THE SEVERAL BREEDS—INDIVIDUAL VARIABILITY—VARIATIONS OF A REMARKABLE NATURE—OSTEOLOGICAL CHARACTERS: SKULL, LOWER JAW, NUMBER OF VERTEBRÆ—CORRELATION OF GROWTH: TONGUE WITH BEAK; EYELIDS AND NOSTRILS WITH WATTLED SKIN—NUMBER OF WING-FEATHERS, AND LENGTH OF WING—COLOUR AND DOWN—WEBBED AND FEATHERED FEET—ON THE EFFECTS OF DISUSE—LENGTH OF FEET IN CORRELATION WITH LENGTH OF BEAK—LENGTH OF STERNUM, SCAPULA, AND FURCULA—LENGTH OF WINGS—SUMMARY ON THE POINTS OF DIFFERENCE IN THE SEVERAL BREEDS ... Page 131

PIGEONS—continued.

ON THE ABORIGINAL PARENT-STOCK OF THE SEVERAL DOMESTIC RACES—HABITS OF LIFE—WILD RACES OF THE ROCK-PIGEON—DOVECOT-PIGEONS—PROOFS OF THE DESCENT OF THE SEVERAL RACES FROM COLUMBA LIVIA—FERTILITY OF THE RACES WHEN CROSSED—REVERSION TO THE PLUMAGE OF THE WILD ROCK-PIGEON—CIRCUMSTANCES FAVOURABLE TO THE FORMATION OF THE RACES—ANTIQUITY AND HISTORY OF THE PRINCIPAL RACES—MANNER OF THEIR FORMATION—SELECTION—UNCONSCIOUS SELECTION—CARE TAKEN BY FANCIERS IN SELECTING THEIR BIRDS—SLIGHTLY DIFFERENT STRAINS GRADUALLY CHANGE INTO WELL-MARKED BREEDS—EXTINCTION OF INTERMEDIATE FORMS—CERTAIN BREEDS REMAIN PERMANENT, WHILST OTHERS CHANGE—SUMMARY ... Page 180

{v}

FOWLS.

BRIEF DESCRIPTIONS OF THE CHIEF BREEDS—ARGUMENTS IN FAVOUR OF THEIR DESCENT FROM SEVERAL SPECIES—ARGUMENTS IN FAVOUR OF ALL THE BREEDS HAVING DESCENDED FROM GALLUS BANKIVA—-REVERSION TO THE PARENT-STOCK IN COLOUR—ANALOGOUS VARIATIONS—ANCIENT HISTORY OF THE FOWL—EXTERNAL DIFFERENCES BETWEEN THE SEVERAL BREEDS—EGGS—CHICKENS—SECONDARY SEXUAL CHARACTERS—WING- AND TAIL-FEATHERS, VOICE, DISPOSITION, ETC.—OSTEOLOGICAL DIFFERENCES IN THE SKULL, VERTEBRÆ, ETC.—EFFECTS OF USE AND DISUSE ON CERTAIN PARTS—CORRELATION OF GROWTH ... Page 225

DUCKS—GOOSE—PEACOCK—TURKEY—GUINEA-FOWL—CANARY-BIRD—GOLD-FISH—HIVE-BEES—SILK-MOTHS.

DUCKS, SEVERAL BREEDS OF—PROGRESS OF DOMESTICATION—ORIGIN OF, FROM THE COMMON WILD-DUCK—DIFFERENCES IN THE DIFFERENT BREEDS—OSTEOLOGICAL DIFFERENCES—EFFECTS OF USE AND DISUSE ON THE LIMB-BONES.

GOOSE, ANCIENTLY DOMESTICATED—LITTLE VARIATION OF—SEBASTOPOL BREED.

PEACOCK, ORIGIN OF BLACK-SHOULDERED BREED.

TURKEY, BREEDS OF—CROSSED WITH THE UNITED STATES SPECIES—EFFECTS OF CLIMATE ON.

GUINEA-FOWL, CANARY-BIRD, GOLD-FISH, HIVE-BEES.

SILK-MOTHS, SPECIES AND BREEDS OF—ANCIENTLY DOMESTICATED—CARE IN THEIR SELECTION—DIFFERENCES IN THE DIFFERENT RACES—IN THE EGG, CATERPILLAR, AND COCOON STATES—INHERITANCE OF CHARACTERS—IMPERFECT WINGS—LOST INSTINCTS—CORRELATED CHARACTERS ... Page 276

CULTIVATED PLANTS: CEREAL AND CULINARY PLANTS.

PRELIMINARY REMARKS ON THE NUMBER AND PARENTAGE OF CULTIVATED PLANTS—FIRST STEPS IN CULTIVATION—GEOGRAPHICAL DISTRIBUTION OF CULTIVATED PLANTS.

CEREALIA.—DOUBTS ON THE NUMBER OF SPECIES.—WHEAT: VARIETIES OF—INDIVIDUAL VARIABILITY—CHANGED HABITS—SELECTION—ANCIENT HISTORY OF THE VARIETIES.—MAIZE: GREAT VARIATION OF—DIRECT ACTION OF CLIMATE ON.

CULINARY PLANTS.—CABBAGES: VARIETIES OF, IN FOLIAGE AND STEMS, BUT NOT IN OTHER PARTS—PARENTAGE OF—OTHER SPECIES OF BRASSICA.—PEAS: AMOUNT OF DIFFERENCE IN THE SEVERAL KINDS, CHIEFLY IN THE PODS AND SEED—SOME VARIETIES CONSTANT, SOME HIGHLY VARIABLE—DO NOT INTERCROSS.—BEANS.—POTATOES: NUMEROUS VARIETIES OF—DIFFERING LITTLE, EXCEPT IN THE TUBERS—CHARACTERS INHERITED ... Page 305

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PLANTS continued—FRUITS—ORNAMENTAL TREES—FLOWERS.

FRUITS.—GRAPES—VARY IN ODD AND TRIFLING PARTICULARS.—MULBERRY.—THE ORANGE GROUP—SINGULAR RESULTS FROM CROSSING.—PEACH AND NECTARINE—BUD-VARIATION—ANALOGOUS VARIATION—RELATION TO THE ALMOND.—APRICOT.—PLUMS—VARIATION IN THEIR STONES.—CHERRIES—SINGULAR VARIETIES OF.—APPLE.—PEAR.—STRAWBERRY—INTERBLENDING OF THE ORIGINAL FORMS.—GOOSEBERRY—STEADY INCREASE IN SIZE OF THE FRUIT—VARIETIES OF.—WALNUT.—NUT.—CUCURBITACEOUS PLANTS—WONDERFUL VARIATION OF.

ORNAMENTAL TREES—THEIR VARIATION IN DEGREE AND KIND—ASH-TREE—SCOTCH-FIR—HAWTHORN.

FLOWERS—MULTIPLE ORIGIN OF MANY KINDS—VARIATION IN CONSTITUTIONAL PECULIARITIES—KIND OF VARIATION.—ROSES—SEVERAL SPECIES CULTIVATED.—PANSY.—DAHLIA.—HYACINTH, HISTORY AND VARIATION OF ... Page 332

ON BUD-VARIATION, AND ON CERTAIN ANOMALOUS MODES OF REPRODUCTION AND VARIATION.

BUD-VARIATIONS IN THE PEACH, PLUM, CHERRY, VINE, GOOSEBERRY, CURRANT, AND BANANA, AS SHOWN BY THE MODIFIED FRUIT—IN FLOWERS: CAMELLIAS, AZALEAS, CHRYSANTHEMUMS, ROSES, ETC.—ON THE RUNNING OF THE COLOUR IN CARNATIONS—BUD-VARIATIONS IN LEAVES—VARIATIONS BY SUCKERS, TUBERS, AND BULBS—ON THE BREAKING OF TULIPS—BUD-VARIATIONS GRADUATE INTO CHANGES CONSEQUENT ON CHANGED CONDITIONS OF LIFE—CYTISUS ADAMI, ITS ORIGIN AND TRANSFORMATION—ON THE UNION OF TWO DIFFERENT EMBRYOS IN ONE SEED—THE TRIFACIAL ORANGE—ON REVERSION BY BUDS IN HYBRIDS AND MONGRELS—ON THE PRODUCTION OF MODIFIED BUDS BY THE GRAFTING OF ONE VARIETY OR SPECIES ON ANOTHER—ON THE DIRECT OR IMMEDIATE ACTION OF FOREIGN POLLEN ON THE MOTHER-PLANT—ON THE EFFECTS IN FEMALE ANIMALS OF A FIRST IMPREGNATION ON THE SUBSEQUENT OFFSPRING—CONCLUSION AND SUMMARY ... Page 373

CHAPTER XII.

INHERITANCE.

WONDERFUL NATURE OF INHERITANCE—PEDIGREES OF OUR DOMESTICATED ANIMALS—INHERITANCE NOT DUE TO CHANCE—TRIFLING CHARACTERS INHERITED—DISEASES INHERITED—PECULIARITIES IN THE EYE INHERITED—DISEASES IN THE HORSE—LONGEVITY AND VIGOUR—ASYMMETRICAL DEVIATIONS OF STRUCTURE—POLYDACTYLISM AND REGROWTH OF SUPERNUMERARY DIGITS AFTER AMPUTATION—CASES OF SEVERAL CHILDREN SIMILARLY AFFECTED FROM NON-AFFECTED PARENTS—WEAK AND FLUCTUATING INHERITANCE: IN WEEPING TREES, IN DWARFNESS, COLOUR OF FRUIT AND FLOWERS, COLOUR OF HORSES—NON-INHERITANCE IN CERTAIN CASES—INHERITANCE OF STRUCTURE AND HABITS OVERBORNE BY HOSTILE CONDITIONS OF LIFE, BY INCESSANTLY RECURRING VARIABILITY, AND BY REVERSION—CONCLUSION ... Page 1

CHAPTER XIII.

INHERITANCE continued—REVERSION OR ATAVISM.

DIFFERENT FORMS OF REVERSION—IN PURE OR UNCROSSED BREEDS, AS IN PIGEONS, FOWLS, HORNLESS CATTLE AND SHEEP, IN CULTIVATED PLANTS—REVERSION IN FERAL ANIMALS AND PLANTS—REVERSION IN CROSSED VARIETIES AND SPECIES—REVERSION THROUGH BUD-PROPAGATION, AND BY SEGMENTS IN THE SAME FLOWER OR FRUIT—IN DIFFERENT PARTS OF THE BODY IN THE SAME ANIMAL—THE ACT OF CROSSING A DIRECT CAUSE OF REVERSION, VARIOUS CASES OF, WITH INSTINCTS—OTHER PROXIMATE CAUSES OF REVERSION—LATENT CHARACTERS—SECONDARY SEXUAL CHARACTERS—UNEQUAL DEVELOPMENT OF THE TWO SIDES OF THE BODY—APPEARANCE WITH ADVANCING AGE OF CHARACTERS DERIVED FROM A CROSS—THE GERM WITH ALL ITS LATENT CHARACTERS A WONDERFUL OBJECT—MONSTROSITIES—PELORIC FLOWERS DUE IN SOME CASES TO REVERSION ... Page 28

CHAPTER XIV.

INHERITANCE continued—FIXEDNESS OF CHARACTER—PREPOTENCY—SEXUAL LIMITATION—CORRESPONDENCE OF AGE.

FIXEDNESS OF CHARACTER APPARENTLY NOT DUE TO ANTIQUITY OF INHERITANCE—PREPOTENCY OF TRANSMISSION IN INDIVIDUALS OF THE SAME FAMILY, IN CROSSED BREEDS AND SPECIES; OFTEN STRONGER IN ONE SEX THAN THE OTHER; SOMETIMES DUE TO THE SAME CHARACTER BEING PRESENT AND VISIBLE IN ONE BREED AND LATENT IN THE OTHER—INHERITANCE AS LIMITED BY SEX—NEWLY-ACQUIRED CHARACTERS IN OUR DOMESTICATED ANIMALS OFTEN TRANSMITTED BY ONE SEX ALONE, SOMETIMES LOST BY ONE SEX ALONE—INHERITANCE AT CORRESPONDING PERIODS OF LIFE—THE IMPORTANCE OF THE PRINCIPLE WITH RESPECT TO EMBRYOLOGY; AS EXHIBITED IN DOMESTICATED ANIMALS; AS EXHIBITED IN THE APPEARANCE AND DISAPPEARANCE OF INHERITED DISEASES; SOMETIMES SUPERVENING EARLIER IN THE CHILD THAN IN THE PARENT—SUMMARY OF THE THREE PRECEDING CHAPTERS ... Page 62

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CHAPTER XV.

ON CROSSING.

FREE INTERCROSSING OBLITERATES THE DIFFERENCES BETWEEN ALLIED BREEDS—WHEN THE NUMBERS OF TWO COMMINGLING BREEDS ARE UNEQUAL, ONE ABSORBS THE OTHER—THE RATE OF ABSORPTION DETERMINED BY PREPOTENCY OF TRANSMISSION, BY THE CONDITIONS OF LIFE, AND BY NATURAL SELECTION—ALL ORGANIC BEINGS OCCASIONALLY INTERCROSS; APPARENT EXCEPTIONS—ON CERTAIN CHARACTERS INCAPABLE OF FUSION; CHIEFLY OR EXCLUSIVELY THOSE WHICH HAVE SUDDENLY APPEARED IN THE INDIVIDUAL—ON THE MODIFICATION OF OLD RACES, AND THE FORMATION OF NEW RACES, BY CROSSING—SOME CROSSED RACES HAVE BRED TRUE FROM THEIR FIRST PRODUCTION—ON THE CROSSING OF DISTINCT SPECIES IN RELATION TO THE FORMATION OF DOMESTIC RACES ... Page 85

CHAPTER XVI.

CAUSES WHICH INTERFERE WITH THE FREE CROSSING OF VARIETIES—INFLUENCE OF DOMESTICATION ON FERTILITY.

DIFFICULTIES IN JUDGING OF THE FERTILITY OF VARIETIES WHEN CROSSED—VARIOUS CAUSES WHICH KEEP VARIETIES DISTINCT, AS THE PERIOD OF BREEDING AND SEXUAL PREFERENCE—VARIETIES OF WHEAT SAID TO BE STERILE WHEN CROSSED—VARIETIES OF MAIZE, VERBASCUM, HOLLYHOCK, GOURDS, MELONS, AND TOBACCO, RENDERED IN SOME DEGREE MUTUALLY STERILE—DOMESTICATION ELIMINATES THE TENDENCY TO STERILITY NATURAL TO SPECIES WHEN CROSSED—ON THE INCREASED FERTILITY OF UNCROSSED ANIMALS AND PLANTS FROM DOMESTICATION AND CULTIVATION ... Page 100

CHAPTER XVII.

ON THE GOOD EFFECTS OF CROSSING, AND ON THE EVIL EFFECTS OF CLOSE INTERBREEDING.

DEFINITION OF CLOSE INTERBREEDING—AUGMENTATION OF MORBID TENDENCIES—GENERAL EVIDENCE ON THE GOOD EFFECTS DERIVED FROM CROSSING, AND ON THE EVIL EFFECTS FROM CLOSE INTERBREEDING—CATTLE, CLOSELY INTERBRED; HALF-WILD CATTLE LONG KEPT IN THE SAME PARKS—SHEEP—FALLOW-DEER—DOGS—RABBITS—PIGS—MAN, ORIGIN OF HIS ABHORRENCE OF INCESTUOUS MARRIAGES—FOWLS—PIGEONS—HIVE-BEES—PLANTS, GENERAL CONSIDERATIONS ON THE BENEFITS DERIVED FROM CROSSING—MELONS, FRUIT-TREES, PEAS, CABBAGES, WHEAT, AND FOREST-TREES—ON THE INCREASED SIZE OF HYBRID PLANTS, NOT EXCLUSIVELY DUE TO THEIR STERILITY—ON CERTAIN PLANTS WHICH EITHER NORMALLY OR ABNORMALLY ARE SELF-IMPOTENT, BUT ARE FERTILE, BOTH ON THE MALE AND FEMALE SIDE, WHEN CROSSED WITH DISTINCT INDIVIDUALS EITHER OF THE SAME OR ANOTHER SPECIES—CONCLUSION ... Page 114

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CHAPTER XVIII.

ON THE ADVANTAGES AND DISADVANTAGES OF CHANGED CONDITIONS OF LIFE: STERILITY FROM VARIOUS CAUSES.

ON THE GOOD DERIVED FROM SLIGHT CHANGES IN THE CONDITIONS OF LIFE—STERILITY FROM CHANGED CONDITIONS, IN ANIMALS, IN THEIR NATIVE COUNTRY AND IN MENAGERIES—MAMMALS, BIRDS, AND INSECTS—LOSS OF SECONDARY SEXUAL CHARACTERS AND OF INSTINCTS—CAUSES OF STERILITY—STERILITY OF DOMESTICATED ANIMALS FROM CHANGED CONDITIONS—SEXUAL INCOMPATIBILITY OF INDIVIDUAL ANIMALS—STERILITY OF PLANTS FROM CHANGED CONDITIONS OF LIFE—CONTABESCENCE OF THE ANTHERS—MONSTROSITIES AS A CAUSE OF STERILITY—DOUBLE FLOWERS—SEEDLESS FRUIT—STERILITY FROM THE EXCESSIVE DEVELOPMENT OF THE ORGANS OF VEGETATION—FROM LONG-CONTINUED PROPAGATION BY BUDS—INCIPIENT STERILITY THE PRIMARY CAUSE OF DOUBLE FLOWERS AND SEEDLESS FRUIT ... Page 145

CHAPTER XIX.

SUMMARY OF THE FOUR LAST CHAPTERS, WITH REMARKS ON HYBRIDISM.

ON THE EFFECTS OF CROSSING—THE INFLUENCE OF DOMESTICATION ON FERTILITY—CLOSE INTERBREEDING—GOOD AND EVIL RESULTS FROM CHANGED CONDITIONS OF LIFE—VARIETIES WHEN CROSSED NOT INVARIABLY FERTILE—ON THE DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND VARIETIES—CONCLUSIONS WITH RESPECT TO HYBRIDISM—LIGHT THROWN ON HYBRIDISM BY THE ILLEGITIMATE PROGENY OF DIMORPHIC AND TRIMORPHIC PLANTS—STERILITY OF CROSSED SPECIES DUE TO DIFFERENCES CONFINED TO THE REPRODUCTIVE SYSTEM—NOT ACCUMULATED THROUGH NATURAL SELECTION—REASONS WHY DOMESTIC VARIETIES ARE NOT MUTUALLY STERILE—TOO MUCH STRESS HAS BEEN LAID ON THE DIFFERENCE IN FERTILITY BETWEEN CROSSED SPECIES AND CROSSED VARIETIES—CONCLUSION ... Page 173

CHAPTER XX.

SELECTION BY MAN.

SELECTION A DIFFICULT ART—METHODICAL, UNCONSCIOUS, AND NATURAL SELECTION—RESULTS OF METHODICAL SELECTION—CARE TAKEN IN SELECTION—SELECTION WITH PLANTS—SELECTION CARRIED ON BY THE ANCIENTS, AND BY SEMI-CIVILISED PEOPLE—UNIMPORTANT CHARACTERS OFTEN ATTENDED TO—UNCONSCIOUS SELECTION—AS CIRCUMSTANCES SLOWLY CHANGE, SO HAVE OUR DOMESTICATED ANIMALS CHANGED THROUGH THE ACTION OF UNCONSCIOUS SELECTION—INFLUENCE OF DIFFERENT BREEDERS ON THE SAME SUB-VARIETY—PLANTS AS AFFECTED BY UNCONSCIOUS SELECTION—EFFECTS OF SELECTION AS SHOWN BY THE GREAT AMOUNT OF DIFFERENCE IN THE PARTS MOST VALUED BY MAN ... Page 192

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CHAPTER XXI.

SELECTION—continued.

NATURAL SELECTION AS AFFECTING DOMESTIC PRODUCTIONS—CHARACTERS WHICH APPEAR OF TRIFLING VALUE OFTEN OF REAL IMPORTANCE—CIRCUMSTANCES FAVOURABLE TO SELECTION BY MAN—FACILITY IN PREVENTING CROSSES, AND THE NATURE OF THE CONDITIONS—CLOSE ATTENTION AND PERSEVERANCE INDISPENSABLE—THE PRODUCTION OF A LARGE NUMBER OF INDIVIDUALS ESPECIALLY FAVOURABLE—WHEN NO SELECTION IS APPLIED, DISTINCT RACES ARE NOT FORMED—HIGHLY-BRED ANIMALS LIABLE TO DEGENERATION—TENDENCY IN MAN TO CARRY THE SELECTION OF EACH CHARACTER TO AN EXTREME POINT, LEADING TO DIVERGENCE OF CHARACTER, RARELY TO CONVERGENCE—CHARACTERS CONTINUING TO VARY IN THE SAME DIRECTION IN WHICH THEY HAVE ALREADY VARIED—DIVERGENCE OF CHARACTER, WITH THE EXTINCTION OF INTERMEDIATE VARIETIES, LEADS TO DISTINCTNESS IN OUR DOMESTIC RACES—LIMIT TO THE POWER OF SELECTION—LAPSE OF TIME IMPORTANT—MANNER IN WHICH DOMESTIC RACES HAVE ORIGINATED—SUMMARY ... Page 224

CHAPTER XXII.

CAUSES OF VARIABILITY.

VARIABILITY DOES NOT NECESSARILY ACCOMPANY REPRODUCTION—CAUSES ASSIGNED BY VARIOUS AUTHORS—INDIVIDUAL DIFFERENCES—VARIABILITY OF EVERY KIND DUE TO CHANGED CONDITIONS OF LIFE—ON THE NATURE OF SUCH CHANGES—CLIMATE, FOOD, EXCESS OF NUTRIMENT—SLIGHT CHANGES SUFFICIENT—EFFECTS OF GRAFTING ON THE VARIABILITY OF SEEDLING-TREES—DOMESTIC PRODUCTIONS BECOME HABITUATED TO CHANGED CONDITIONS—ON THE ACCUMULATIVE ACTION OF CHANGED CONDITIONS—CLOSE INTERBREEDING AND THE IMAGINATION OF THE MOTHER SUPPOSED TO CAUSE VARIABILITY—CROSSING AS A CAUSE OF THE APPEARANCE OF NEW CHARACTERS—VARIABILITY FROM THE COMMINGLING OF CHARACTERS AND FROM REVERSION—ON THE MANNER AND PERIOD OF ACTION OF THE CAUSES WHICH EITHER DIRECTLY, OR INDIRECTLY THROUGH THE REPRODUCTIVE SYSTEM, INDUCE VARIABILITY ... Page 250

CHAPTER XXIII.

DIRECT AND DEFINITE ACTION OF THE EXTERNAL CONDITIONS OF LIFE.

SLIGHT MODIFICATIONS IN PLANTS FROM THE DEFINITE ACTION OF CHANGED CONDITIONS, IN SIZE, COLOUR, CHEMICAL PROPERTIES, AND IN THE STATE OF THE TISSUES—LOCAL DISEASES—CONSPICUOUS MODIFICATIONS FROM CHANGED CLIMATE OR FOOD, ETC.—PLUMAGE OF BIRDS AFFECTED BY PECULIAR NUTRIMENT, AND BY THE INOCULATION OF POISON—LAND-SHELLS—MODIFICATIONS OF ORGANIC BEINGS IN A STATE OF NATURE THROUGH THE DEFINITE ACTION OF EXTERNAL CONDITIONS—COMPARISON OF AMERICAN AND EUROPEAN TREES—GALLS—EFFECTS OF PARASITIC FUNGI—CONSIDERATIONS OPPOSED TO THE BELIEF IN THE POTENT INFLUENCE OF CHANGED EXTERNAL CONDITIONS—PARALLEL SERIES OF VARIETIES—AMOUNT OF VARIATION DOES NOT CORRESPOND WITH THE DEGREE OF CHANGE IN THE CONDITIONS—BUD-VARIATION—MONSTROSITIES PRODUCED BY UNNATURAL TREATMENT—SUMMARY ... Page 271

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CHAPTER XXIV.

LAWS OF VARIATION—USE AND DISUSE, ETC.

NISUS FORMATIVUS, OR THE CO-ORDINATING POWER OF THE ORGANISATION—ON THE EFFECTS OF THE INCREASED USE AND DISUSE OF ORGANS—CHANGED HABITS OF LIFE—ACCLIMATISATION WITH ANIMALS AND PLANTS—VARIOUS METHODS BY WHICH THIS CAN BE EFFECTED—ARRESTS OF DEVELOPMENT—RUDIMENTARY ORGANS ... Page 293

CHAPTER XXV.

LAWS OF VARIATION, continued—CORRELATED VARIABILITY.

EXPLANATION OF TERM—CORRELATION AS CONNECTED WITH DEVELOPMENT—MODIFICATIONS CORRELATED WITH THE INCREASED OR DECREASED SIZE OF PARTS—CORRELATED VARIATION OF HOMOLOGOUS PARTS—FEATHERED FEET IN BIRDS ASSUMING THE STRUCTURE OF THE WINGS—CORRELATION BETWEEN THE HEAD AND THE EXTREMITIES—BETWEEN THE SKIN AND DERMAL APPENDAGES—BETWEEN THE ORGANS OF SIGHT AND HEARING—CORRELATED MODIFICATIONS IN THE ORGANS OF PLANTS—CORRELATED MONSTROSITIES—CORRELATION BETWEEN THE SKULL AND EARS—SKULL AND CREST OF FEATHERS—SKULL AND HORNS—CORRELATION OF GROWTH COMPLICATED BY THE ACCUMULATED EFFECTS OF NATURAL SELECTION—COLOUR AS CORRELATED WITH CONSTITUTIONAL PECULIARITIES ... Page 319

CHAPTER XXVI.

LAWS OF VARIATION, continued—SUMMARY.

ON THE AFFINITY AND COHESION OF HOMOLOGOUS PARTS—ON THE VARIABILITY OF MULTIPLE AND HOMOLOGOUS PARTS—COMPENSATION OF GROWTH—MECHANICAL PRESSURE—RELATIVE POSITION OF FLOWERS WITH RESPECT TO THE AXIS OF THE PLANT, AND OF SEEDS IN THE CAPSULE, AS INDUCING VARIATION—ANALOGOUS OR PARALLEL VARIETIES—SUMMARY OF THE THREE LAST CHAPTERS ... Page 339

CHAPTER XXVII.

PROVISIONAL HYPOTHESIS OF PANGENESIS.

PRELIMINARY REMARKS—FIRST PART:—THE FACTS TO BE CONNECTED UNDER A SINGLE POINT OF VIEW, NAMELY, THE VARIOUS KINDS OF REPRODUCTION—THE DIRECT ACTION OF THE MALE ELEMENT ON THE FEMALE—DEVELOPMENT—THE FUNCTIONAL INDEPENDENCE OF THE ELEMENTS OR UNITS OF THE BODY—VARIABILITY—INHERITANCE—REVERSION.

SECOND PART:—STATEMENT OF THE HYPOTHESIS—HOW FAR THE NECESSARY ASSUMPTIONS ARE IMPROBABLE—EXPLANATION BY AID OF THE HYPOTHESIS OF THE SEVERAL CLASSES OF FACTS SPECIFIED IN THE FIRST PART—CONCLUSION ... Page 357

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CHAPTER XXVIII.

CONCLUDING REMARKS.

DOMESTICATION—NATURE AND CAUSES OF VARIABILITY—SELECTION—DIVERGENCE AND DISTINCTNESS OF CHARACTER—EXTINCTION OF RACES—CIRCUMSTANCES FAVOURABLE TO SELECTION BY MAN—ANTIQUITY OF CERTAIN RACES—THE QUESTION WHETHER EACH PARTICULAR VARIATION HAS BEEN SPECIALLY PREORDAINED ... Page 405

Index ... Page 433

Introduction

Page 1–6

CHAPTER I.
HABITS OF WORMS.

Nature of the sites inhabited—Can live long under water—Nocturnal—Wander about at night—Often lie close to the mouths of their burrows, and are thus destroyed in large numbers by birds—Structure—Do not possess eyes, but can distinguish between light and darkness—Retreat rapidly when brightly illuminated, not by a reflex action—Power of attention—Sensitive to heat and cold—Completely deaf—Sensitive to vibrations and to touch—Feeble power of smell—Taste—Mental qualities—Nature of food—Omnivorous—Digestion—Leaves before being swallowed, moistened with a fluid of the nature of the pancreatic secretion—Extra-stomachal digestion—Calciferous glands, structure of—Calcareous concretions formed in the anterior pair of glands—The calcareous matter primarily an excretion, but secondarily serves to neutralise the acids generated during the digestive process.

7–15

CHAPTER II.
HABITS OF WORMS—continued.

Manner in which worms seize objects—Their power of suction—The instinct of plugging up the mouths of their burrows—Stones piled over the burrows—The advantages thus gained—Intelligence shown by worms in their manner of plugging up their burrows—Various kinds of leaves and other objects thus used—Triangles of paper—Summary of reasons for believing that worms exhibit some intelligence—Means by which they excavate their burrows, by pushing away the earth and swallowing it—Earth also swallowed for the nutritious matter which it contains—Depth to which worms burrow, and the construction of their burrows—Burrows lined with castings, and in the upper part with leaves—The lowest part paved with little stones or seeds—Manner in which the castings are ejected—The collapse of old burrows—Distribution of worms—Tower-like castings in Bengal—Gigantic castings on the Nilgiri Mountains—Castings ejected in all countries.

52–120

CHAPTER III.
THE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE SURFACE.

Rate at which various objects strewed on the surface of grass-fields are covered up by the castings of worms—The burial of a paved path—The slow subsidence of great stones left on the surface—The number of worms which live within a given space—The weight of earth ejected from a burrow, and from all the burrows within a given space—The thickness of the layer of mould which the castings on a given space would form within a given time if uniformly spread out—The slow rate at which mould can increase to a great thickness—Conclusion.

121–163

CHAPTER IV.
THE PART WHICH WORMS HAVE PLAYED IN THE BURIAL OF ANCIENT BUILDINGS.

The accumulation of rubbish on the sites of great cities independent of the action of worms—The burial of a Roman villa at Abinger—The floors and walls penetrated by worms—Subsidence of a modern pavement—The buried pavement at Beaulieu Abbey—Roman villas at Chedworth and Brading—The remains of the Roman town at Silchester—The nature of the débris by which the remains are covered—The penetration of the tesselated floors and walls by worms—Subsidence of the floors—Thickness of the mould—The old Roman city of Wroxeter—Thickness of the mould—Depth of the foundations of some of the Buildings—Conclusion.

164–208

CHAPTER V.
THE ACTION OF WORMS IN THE DENUDATION OF THE LAND.

Evidence of the amount of denudation which the land has undergone—Sub-aerial denudation—The deposition of dust—Vegetable mould, its dark colour and fine texture largely due to the action of worms—The disintegration of rocks by the humus-acids—Similar acids apparently generated within the bodies of worms—The action of these acids facilitated by the continued movement of the particles of earth—A thick bed of mould checks the disintegration of the underlying soil and rocks.  Particles of stone worn or triturated in the gizzards of worms—Swallowed stones serve as mill-stones—The levigated state of the castings—Fragments of brick in the castings over ancient buildings well rounded.  The triturating power of worms not quite insignificant under a geological point of view.

209–236

CHAPTER VI.
THE DENUDATION OF THE LAND—continued.

Denudation aided by recently ejected castings flowing down inclined grass-covered surfaces—The amount of earth which annually flows downwards—The effect of tropical rain on worm castings—The finest particles of earth washed completely away from castings—The disintegration of dried castings into pellets, and their rolling down inclined surfaces—The formation of little ledges on hill-sides, in part due to the accumulation of disintegrated castings—Castings blown to leeward over level land—An attempt to estimate the amount thus blown—The degradation of ancient encampments and tumuli—The preservation of the crowns and furrows on land anciently ploughed—The formation and amount of mould over the Chalk formation.

237–279

CHAPTER VII.
CONCLUSION.

Summary of the part which worms have played in the history of the world—Their aid in the disintegration of rocks—In the denudation of the land—In the preservation of ancient remains—In the preparation of the soil for the growth of plants—Mental powers of worms—Conclusion.

280–288