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Chapter companions for The Origin of Species by Charles Darwin.

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  1. Chapter 1

    Epigraphs

    The chapter presents three epigraphs from Whewell, Butler, and Bacon, establishing a philosophical foundation for the work by arguing that natural laws, not divine interpositions, govern the material world, that the natural presupposes an intelligent agent, and that the pursuit of knowledge in both divinity and philosophy should be endless.

  2. Chapter 2

    An Historical Sketch of the Progress of Opinion on the Origin of Species, Previously to the Publication of the First Edition of This Work

    Darwin provides a historical overview of the development of ideas about the origin of species, from early thinkers like Buffon and Lamarck to his contemporaries. He traces the gradual shift from belief in immutable, separately created species to the concept of descent with modification, highlighting key figures such as Lamarck, Geoffroy Saint-Hilaire, Dr. W. C. Wells, and Mr. Patrick Matthew, who anticipated aspects of natural selection. The sketch culminates with the joint presentation of Darwin's and Wallace's theory in 1858 and the publication of Darwin's own work in 1859.

  3. Chapter 3

    The Origin of Species by Means of Natural Selection

    This chapter introduces the central thesis of Darwin's work: that species are not immutable but have evolved over time through the mechanism of natural selection, which preserves favorable variations in the struggle for life. Darwin sets the stage by discussing variation under domestication and in nature, the struggle for existence, and the principle of natural selection as the primary driver of evolutionary change.

  4. Chapter 4

    I: Variation Under Domestication

    Darwin introduces the concept of variation under domestication, arguing that domestic organisms vary more than wild ones due to changed conditions of life. He discusses causes of variability, the roles of definite and indefinite variation, and the importance of selection by man in shaping domestic breeds. He also addresses the difficulty of distinguishing varieties from species and the origin of domestic races from one or more wild stocks.

  5. Chapter 5

    Causes of Variability

    Darwin explores the causes of variability in domesticated plants and animals, arguing that changed conditions of life, especially over multiple generations, induce variation. He distinguishes between direct effects on the organism and indirect effects through the reproductive system, emphasizing the primacy of the organism's nature over external conditions. He also discusses definite versus indefinite variability and notes that bud variations can occur without sexual reproduction.

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  1. Chapter 6Effects of Habit and of the Use or Disuse of Parts; Correlated Variation; Inheritance
  2. Chapter 7Character of Domestic Varieties; Difficulty of Distinguishing Between Varieties and Species; Origin of Domestic Varieties from One or More Species
  3. Chapter 8Breeds of the Domestic Pigeon, Their Differences and Origin
  4. Chapter 9Principles of Selection Anciently Followed, and Their Effects
  5. Chapter 10Unconscious Selection
  6. Chapter 11Circumstances Favourable to Man’s Power of Selection
  7. Chapter 12II: Variation Under Nature
  8. Chapter 13Individual Differences
  9. Chapter 14Doubtful Species
  10. Chapter 15Wide-Ranging, Much Diffused, and Common Species Vary Most
  11. Chapter 16Species of the Larger Genera in Each Country Vary More Frequently Than the Species of the Smaller Genera
  12. Chapter 17Many of the Species Included Within the Larger Genera Resemble Varieties in Being Very Closely, but Unequally, Related to Each Other, and in Having Restricted Ranges
  13. Chapter 18Summary
  14. Chapter 19III: Struggle for Existence
  15. Chapter 20The Term, Struggle for Existence, Used in a Large Sense
  16. Chapter 21Geometrical Ratio of Increase
  17. Chapter 22Nature of the Checks to Increase
  18. Chapter 23Complex Relations of All Animals and Plants to Each Other in the Struggle for Existence
  19. Chapter 24Struggle for Life Most Severe Between Individuals and Varieties of the Same Species
  20. Chapter 25Natural Selection; or the Survival of the Fittest
  21. Chapter 26Sexual Selection
  22. Chapter 27Illustrations of the Action of Natural Selection, or the Survival of the Fittest
  23. Chapter 28On the Intercrossing of Individuals
  24. Chapter 29Circumstances Favourable for the Production of New Forms Through Natural Selection
  25. Chapter 30Extinction Caused by Natural Selection
  26. Chapter 31Divergence of Character
  27. Chapter 32The Probable Effects of the Action of Natural Selection Through Divergence of Character and Extinction, on the Descendants of a Common Ancestor
  28. Chapter 33On the Degree to Which Organisation Tends to Advance
  29. Chapter 34Convergence of Character
  30. Chapter 35Summary of Chapter
  31. Chapter 36V: Laws of Variation
  32. Chapter 37Effects of the Increased Use and Disuse of Parts, as Controlled by Natural Selection
  33. Chapter 38Acclimatisation
  34. Chapter 39Correlated Variation
  35. Chapter 40Compensation and Economy of Growth
  36. Chapter 41Multiple, Rudimentary, and Lowly-Organised Structures Are Variable
  37. Chapter 42A Part Developed in Any Species in an Extraordinary Degree or Manner, in Comparison with the Same Part in Allied Species, Tends to Be Highly Variable
  38. Chapter 43Specific Characters More Variable Than Generic Characters
  39. Chapter 44Secondary Sexual Characters Variable
  40. Chapter 45Distinct Species Present Analogous Variations, So That a Variety of One Species Often Assumes a Character Proper to an Allied Species, or Reverts to Some of the Characters of an Early Progenitor
  41. Chapter 46Summary
  42. Chapter 47VI: Difficulties of the Theory
  43. Chapter 48On the Absence or Rarity of Transitional Varieties
  44. Chapter 49On the Origin and Transition of Organic Beings with Peculiar Habits and Structure
  45. Chapter 50Organs of Extreme Perfection and Complication
  46. Chapter 51Modes of Transition
  47. Chapter 52Special Difficulties of the Theory of Natural Selection
  48. Chapter 53Organs of Little Apparent Importance, as Affected by Natural Selection
  49. Chapter 54Utilitarian Doctrine, How Far True: Beauty, How Acquired
  50. Chapter 55The Law of Unity of Type and of the Conditions of Existence Embraced by the Theory of Natural Selection
  51. Chapter 56VII: Miscellaneous Objections to the Theory of Natural Selection
  52. Chapter 57Instinct
  53. Chapter 58Inherited Changes of Habit or Instinct in Domesticated Animals
  54. Chapter 59Special Instincts
  55. Chapter 60Instincts of the Cuckoo
  56. Chapter 61Slave-Making Instinct
  57. Chapter 62Cell-Making Instinct of the Hive-Bee
  58. Chapter 63Objections to the Theory of Natural Selection as Applied to Instincts: Neuter and Sterile Insects
  59. Chapter 64Summary
  60. Chapter 65IX: Hybridism
  61. Chapter 66Degrees of Sterility
  62. Chapter 67Laws Governing the Sterility of First Crosses and of Hybrids
  63. Chapter 68Origin and Causes of the Sterility of First Crosses and of Hybrids
  64. Chapter 69Reciprocal Dimorphism and Trimorphism
  65. Chapter 70Fertility of Varieties When Crossed, and of Their Mongrel Offspring, Not Universal
  66. Chapter 71Hybrids and Mongrels Compared, Independently of Their Fertility
  67. Chapter 72Summary of Chapter
  68. Chapter 73On the Imperfection of the Geological Record
  69. Chapter 74On the Lapse of Time, as Inferred from the Rate of Deposition and Extent of Denudation
  70. Chapter 75On the Poorness of Palaeontological Collections
  71. Chapter 76On the Absence of Numerous Intermediate Varieties in Any Single Formation
  72. Chapter 77On the Sudden Appearance of Whole Groups of Allied Species
  73. Chapter 78On the Sudden Appearance of Groups of Allied Species in the Lowest Known Fossiliferous Strata
  74. Chapter 79On the Geological Succession of Organic Beings
  75. Chapter 80On Extinction
  76. Chapter 81On the Forms of Life Changing Almost Simultaneously Throughout the World
  77. Chapter 82On the Affinities of Extinct Species to Each Other, and to Living Forms
  78. Chapter 83On the State of Development of Ancient Compared with Living Forms
  79. Chapter 84On the Succession of the Same Types Within the Same Areas, During the Later Tertiary Periods
  80. Chapter 85Summary of the Preceding and Present Chapters
  81. Chapter 86Geographical Distribution
  82. Chapter 87Single Centres of Supposed Creation
  83. Chapter 88Means of Dispersal
  84. Chapter 89Dispersal During the Glacial Period
  85. Chapter 90Alternate Glacial Periods in the North and South
  86. Chapter 91Geographical Distribution—Continued
  87. Chapter 92Freshwater Productions
  88. Chapter 93On the Inhabitants of Oceanic Islands
  89. Chapter 94Absence of Batrachians and Terrestrial Mammals on Oceanic Islands
  90. Chapter 95On the Relations of the Inhabitants of Islands to Those of the Nearest Mainland
  91. Chapter 96Summary of the Last and Present Chapters
  92. Chapter 97XIV: Mutual Affinities of Organic Beings: Morphology—Embryology—Rudimentary Organs—Classification
  93. Chapter 98Analogical Resemblances
  94. Chapter 99On the Nature of the Affinities Connecting Organic Beings
  95. Chapter 100Morphology
  96. Chapter 101Development and Embryology
  97. Chapter 102Rudimentary, Atrophied, and Aborted Organs
  98. Chapter 103Summary
  99. Chapter 104Recapitulation and Conclusion
  100. Chapter 105Glossary of the Principal Scientific Terms Used in the Present Volume
  101. Chapter 106List of Illustrations
  102. Chapter 107Endnotes