Read Ebook: The Variation of Animals and Plants under Domestication by Darwin Charles

Font size: 10 px 15 px 20 px 25 px 30 px 35 px

Background color: BlackWhiteGrayLight GrayDark GrayDim Gray

Text color: BlackWhiteGrayLight GrayDark GrayDim Gray

Apply/Save settings

Ebook has 7331 lines and 430347 words, and 147 pages

FOREWORD

PREFACE TO THE SECOND EDITION

INTRODUCTION

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

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.

PIGS BELONG TO TWO DISTINCT TYPES, SUS SCROFA AND INDICUS--TORFSCHWEIN--JAPAN PIGS--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.

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.

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--VERtebrae--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.

ENUMERATION AND DESCRIPTION OF THE SEVERAL BREEDS--INDIVIDUAL VARIABILITY--VARIATIONS OF A REMARKABLE NATURE--OSTEOLOGICAL CHARACTERS: SKULL, LOWER JAW, NUMBER OF vertebrae--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 FURCULUM--LENGTH OF WINGS--SUMMARY ON THE POINTS OF DIFFERENCE IN THE SEVERAL BREEDS.

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.

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, VERTEBRAE, ETC--EFFECTS OF USE AND DISUSE ON CERTAIN PARTS--CORRELATION OF GROWTH.

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.

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.

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.

BUD-VARIATION 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--GRAFT-HYBRIDS--ON THE SEGREGATION OF THE PARENTAL CHARACTERS IN SEMINAL HYBRIDS BY BUD-VARIATION--ON THE DIRECT OR IMMEDIATE ACTION OF FOREIGN POLLEN ON THE MOTHER-PLANT--ON THE EFFECTS IN FEMALE ANIMALS OF A PREVIOUS IMPREGNATION ON THE SUBSEQUENT OFFSPRING--CONCLUSION AND SUMMARY.

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.

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.

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.

DEFINITION OF CLOSE INTERBREEDING--AUGMENTATION OF MORBID TENDENCIES--GENERAL EVIDENCE OF 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.

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.

ON THE GOOD DERIVED 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 HETEROSTYLED 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.

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.

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.

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.

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.

EXPLANATION OF TERM CORRELATION--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.

PRELIMINARY REMARKS--FIRST PART: THE FACTS TO BE CONNECTED UNDER A SINGLE POINT OF VIEW, NAMELY, THE VARIOUS KINDS OF REPRODUCTION--RE-GROWTH OF AMPUTATED PARTS--GRAFT-HYBRIDS--THE DIRECT ACTION OF THE MALE ELEMENT ON THE FEMALE--DEVELOPMENT--THE FUNCTIONAL INDEPENDENCE OF THE 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.

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.

INDEX

Figure 1. Dun Devonshire pony, with shoulder, spinal, and leg stripes. Figure 2. Head of Japan or masked pig. Figure 3. Head of wild boar, and of "golden days," a pig of the Yorkshire large breed. Figure 4. Old Irish pig with jaw-appendages. Figure 5. Half-lop rabbit. Figure 6. Skull of wild rabbit. Figure 7. Skull of large lop-eared rabbit. Figure 8. Part of zygomatic arch, showing the projecting end of the malar bone of the auditory meatus, of rabbits. Figure 9. Posterior end of skull, showing the inter-parietal bone, of rabbits. Figure 10. Occipital foramen of rabbits. Figure 11. Skull of half-lop rabbit. Figure 12. Atlas vertebrae of rabbits. Figure 13. Third cervical vertebrae of rabbits. Figure 14. Dorsal vertebrae, from sixth to tenth inclusive, of rabbits. Figure 15. Terminal bone of sternum of rabbits. Figure 16. Acromion of scapula of rabbits. Figure 17. The rock-pigeon, or columba livia. Figure 18. English pouter. Figure 19. English carrier. Figure 20. English barb. Figure 21. English fantail. Figure 22. African owl. Figure 23. Short-faced English tumbler. Figure 24. Skulls of pigeons, viewed laterally. Figure 25. Lower jaws of pigeons, seen from above. Figure 26. Skull of runt, seen from above. Figure 27. Lateral view of jaws of pigeons. Figure 28. Scapulae of pigeons. Figure 29. Furcula of pigeons. Figure 30. Spanish fowl. Figure 31. Hamburgh fowl. Figure 32. Polish fowl. Figure 33. Occipital foramen of the skulls of fowls. Figure 34. Skulls of fowls, viewed from above, a little obliquely. Figure 35. Longitudinal sections of skulls of fowls, viewed laterally. Figure 36. Skull of horned fowl, viewed from above, a little obliquely. Figure 37. Sixth cervical vertebrae of fowls, viewed laterally. Figure 38. Extremity of the furcula of fowls, viewed laterally. Figure 39. Skulls of ducks, viewed laterally, reduced to two-thirds of the natural size. Figure 40. Cervical vertebrae of ducks, of natural size. Figure 41. Pods of the common pea. Figure 42. Peach and almond stones, of natural size, viewed edgeways. Figure 43. Plum stones, of natural size, viewed laterally. FOREWORD

Reassuring as it was, the analogy between natural and artificial selection was far from perfect. The point of Darwin's analogy was to make the idea of natural selection seem plausible by characterizing it as a grander version of a well-known process while emphasizing its efficiency and shaping power. He noted, for example, that some of the prize birds bred by London pigeon fanciers diverged so strikingly in size, plumage, beak shape, flying technique, vocalizations. bone structure, and many other attributes, that if they had been presented to an ornithologist as wild specimens, they would unquestionably have been considered to represent distinct species, perhaps even distinct genera. Darwin argued that if the relatively brief and constrained selective efforts of human breeders had produced such impressive results, it was likely that the more protracted and thorough-going efforts of nature would work still more efficaciously.

But as Darwin acknowledged, there were some fairly obvious reasons why the two processes might diverge. The superior power of natural selection--"Man can act only on external and visible characters: nature . . . can act on . . . the whole machinery of life. Man selects only for his own good; Nature only for that of the being which she tends" --might constitute a difference of kind rather than of degree, as might the much greater stretches of time available for natural selection. Further, although the mechanism of the two processes appeared superficially similar, their outcomes tended to be rather different. Natural selection produced a constantly increasing and diversifying variety of forms; it never reversed or exactly repeated itself. Anyone familiar with artificial selection would have realized that, although new breeds were constantly being developed and although neither improved wheat nor improved cattle showed any tendency to revert to the condition of their aboriginal wild ancestors, the strains produced by human selection were neither as prolific nor as durable as those produced by nature. Indeed, the animals and plants celebrated as the noblest achievements of the breeder's art were especially liable to delicacy and infertility. Highly bred strains, long isolated from others of their species to preserve their genealogical purity, far from serving as a springboard for further variation, often had to be revivified with infusions of less-rarefied blood. Yet any relaxation of reproductive boundaries threatened subsidence into the common run of conspecifics.

Like many other naturalists of his time, Darwin was receptive to the idea of telegony, also known as "the influence of the previous sire." He retailed the famous story of Lord Morton's mare, a chestnut of seven-eighths Arabian blood, whose first foal had been sired by a quagga her owner was attempting to domesticate. It was not surprising that the young hybrid faintly echoed his father's stripes, but the fact that her next two foals, both sired by a black Arabian horse, also seemed to resemble the quagga in this regard, was more remarkable. Darwin pointed out that atavism offered one possible explanation of this phenomenon--infant horses and donkeys often showed evanescent striping, which might indicate the pattern of their ancient shared progenitor--but he was also drawn to the notion that the first male to impregnate a female left some permanent, heritable trace of himself behind. He offered analogous examples from the vegetable kingdom, where the pollen of related varieties of apples, corn, or orchids, could not only produce hybrid offspring but occasionally also physically alter the reproductive tract of the female. Plants also, and more regularly, demonstrated a kind of variability that could arise independently of sexual reproduction, such as "bud variation," whereby what Darwin called a "monstrosity" might appear on a single branch or flower and then be transmitted, sexually or asexually, to future generations.

This problem of the conversion of varieties into species,--that is, the augmentation of the slight differences characteristic of varieties into the greater differences characteristic of species and genera, including the admirable adaptations of each being to its complex organic and inorganic conditions of life,--has been briefly treated in my 'Origin of Species.' It was there shown that all organic beings, without exception, tend to increase at so high a ratio, that no district, no station, not even the whole surface of the land or the whole ocean, would hold the progeny of a single pair after a certain number of generations. The inevitable result is an ever-recurrent Struggle for Existence. It has truly been said that all nature is at war; the strongest ultimately prevail, the weakest fail; and we well know that myriads of forms have disappeared from the face of the earth. If then organic beings in a state of nature vary even in a slight degree, owing to changes in the surrounding conditions, of which we have abundant geological evidence, or from any other cause; if, in the long course of ages, inheritable variations ever arise in any way advantageous to any being under its excessively complex and changing relations of life; and it would be a strange fact if beneficial variations did never arise, seeing how many have arisen which man has taken advantage of for his own profit or pleasure; if then these contingencies ever occur, and I do not see how the probability of their occurrence can be doubted, then the severe and often-recurrent struggle for existence will determine that those variations, however slight, which are favourable shall be preserved or selected, and those which are unfavourable shall be destroyed.

This preservation, during the battle for life, of varieties which possess any advantage in structure, constitution, or instinct, I have called Natural Selection; and Mr. Herbert Spencer has well expressed the same idea by the Survival of the Fittest. The term "natural selection" is in some respects a bad one, as it seems to imply conscious choice; but this will be disregarded after a little familiarity. No one objects to chemists speaking of "elective affinity;" and certainly an acid has no more choice in combining with a base, than the conditions of life have in determining whether or not a new form be selected or preserved. The term is so far a good one as it brings into connection the production of domestic races by man's power of selection, and the natural preservation of varieties and species in a state of nature. For brevity sake I sometimes speak of natural selection as an intelligent power;--in the same way as astronomers speak of the attraction of gravity as ruling the movements of the planets, or as agriculturists speak of man making domestic races by his power of selection. In the one case, as in the other, selection does nothing without variability, and this depends in some manner on the action of the surrounding circumstances on the organism. I have, also, often personified the word Nature; for I have found it difficult to avoid this ambiguity; but I mean by nature only the aggregate action and product of many natural laws,--and by laws only the ascertained sequence of events.

It has been shown from many facts that the largest amount of life can be supported on each area, by great diversification or divergence in the structure and constitution of its inhabitants. We have, also, seen that the continued production of new forms through natural selection, which implies that each new variety has some advantage over others, inevitably leads to the extermination of the older and less improved forms. These latter are almost necessarily intermediate in structure, as well as in descent, between the last-produced forms and their original parent-species. Now, if we suppose a species to produce two or more varieties, and these in the course of time to produce other varieties, the principal of good being derived from diversification of structure will generally lead to the preservation of the most divergent varieties; thus the lesser differences characteristic of varieties come to be augmented into the greater differences characteristic of species, and, by the extermination of the older intermediate forms, new species end by being distinctly defined objects. Thus, also, we shall see how it is that organic beings can be classed by what is called a natural method in distinct groups--species under genera, and genera under families.

As all the inhabitants of each country may be said, owing to their high rate of reproduction, to be striving to increase in numbers; as each form comes into competition with many other forms in the struggle for life,--for destroy any one and its place will be seized by others; as every part of the organisation occasionally varies in some slight degree, and as natural selection acts exclusively by the preservation of variations which are advantageous under the excessively complex conditions to which each being is exposed, no limit exists to the number, singularity, and perfection of the contrivances and co-adaptations which may thus be produced. An animal or a plant may thus slowly become related in its structure and habits in the most intricate manner to many other animals and plants, and to the physical conditions of its home. Variations in the organisation will in some cases be aided by habit, or by the use and disuse of parts, and they will be governed by the direct action of the surrounding physical conditions and by correlation of growth.

On the principles here briefly sketched out, there is no innate or necessary tendency in each being to its own advancement in the scale of organisation. We are almost compelled to look at the specialisation or differentiation of parts or organs for different functions as the best or even sole standard of advancement; for by such division of labour each function of body and mind is better performed. And as natural selection acts exclusively through the preservation of profitable modifications of structure, and as the conditions of life in each area generally become more and more complex from the increasing number of different forms which inhabit it and from most of these forms acquiring a more and more perfect structure, we may confidently believe, that, on the whole, organisation advances. Nevertheless a very simple form fitted for very simple conditions of life might remain for indefinite ages unaltered or unimproved; for what would it profit an infusorial animalcule, for instance, or an intestinal worm, to become highly organised? Members of a high group might even become, and this apparently has often occurred, fitted for simpler conditions of life; and in this case natural selection would tend to simplify or degrade the organisation, for complicated mechanism for simple actions would be useless or even disadvantageous.

The arguments opposed to the theory of Natural Selection, have been discussed in my 'Origin of Species,' as far as the size of that work permitted, under the following heads: the difficulty in understanding how very simple organs have been converted by small and graduated steps into highly perfect and complex organs; the marvellous facts of Instinct; the whole question of Hybridity; and, lastly, the absence in our known geological formations of innumerable links connecting all allied species. Although some of these difficulties are of great weight, we shall see that many of them are explicable on the theory of natural selection, and are otherwise inexplicable.

Share on: WhatsApp @Hash Facebook Tweet