The Variation of Animals and Plants Under Domestication

Charles Darwin

2nd edition, 1875

Book I


Chapter I: 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 Feet--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

Chapter II: 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 Horse Most Frequently 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.

Chapter III: Pigs--Cattle--Sheep--Goats.

Pigs Belong to Two Distinct Types, Sus Scrofa and Ludicus--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 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

Chapter IV: 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 Analagous 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

Chapter V: Domestic Pigeons.

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; Eye Lids 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

Chapter VI: 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, While Others Change--Summary

Chapter VII: 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 Bankia?--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

Chapter VIII: Duck--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-Bee.

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

Chapter IX: 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--Select on--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--Differ Little Except in the Tubers--Characters inherited

Chapter X: 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

Chapter XI: On Bud-Variation, and on Certain Anomalous Modes of Reproduction and Variation.

Bud-Variation in the E 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 of A Previous Impregnation on the Subsequent offspring of Female Animals--Conclusion and Summary

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--Polydactilism 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

Book II

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 Rough 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

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 Ted in the Appearance and Disappearance of inherited Diseases Sometimes Supervening Earlier in the Child than in the Parent--Summary of the Three Preceding Chapters.

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 Adsorption 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 Backs, 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

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.

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 of the Good Effects Derived from Crossing, and on the Evil Effects of Close interbreeding--Cattle, Closely interbred; Half-Wild Cattle Long Kept N 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

Chapter XVIII: On the Advantages and Disadvantages of Changed Conditions of Life: Sterility From Various Causes.

0f 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--Seed-- Less 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

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 Ate 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

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 Ox 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

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

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

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

Chapter XXIV: Laws of Variation--Use and Disuse, Etc.

Nisus Formativus, or the Co-ordinating Power of the organization--On the Effects of the increased Use and Disuse of organs--Changed Habits of Life .--Acclimatization With Animals and Plants--Various Methods By Which This Can Be Effected--Arrests of Development--Rudimentary organ's.

Chapter XXV: Laws of Variation, Continued--Correlated Variability.

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

Chapter XXVI: Laws of Variation, continued--Summary.

The Fusion of Homologous Parts--the Variability of Multiple and Homologous Parts--Compensation of Growth--Mechanical Pressure--Relative Position of Flowers With Respect to the Axis, and of Seeds in the Ovary, As inducing Variation--Analogous or Parallel Varieties--Summary of the Three Last Chapters

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 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

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.