Objections to Forbes' Theory of Polarity Rudimentary Organs Conclusion II.--_On the Tendency of Varieties to depart indefinitely from the Original Type._ Pp. 26-44 Instability of Varieties supposed to prove the permanent distinctness of Species The Struggle for Existence The Law of Population of Species The Abundance or Rarity of a Species dependent upon its more or less perfect Adaptation to the Conditions of Existence Useful Variations will tend to Increase, useless or hurtful Variations to Diminish Superior Varieties will ultimately extirpate the Original Species The Partial Reversion of Domesticated Varieties explained Lamarck's Hypothesis very different from that now advanced Conclusion III.--_Mimicry, and other Protective Resemblances among Animals._ Pp. 45-129 Test of true and false Theories Importance of the Principle of Utility Popular Theories of Colour in Animals Importance of Concealment as influencing Colour Special modifications of Colour Theory of Protective Colouring Objection that Colour as being dangerous should not exist in Nature Mimicry Mimicry among Lepidoptera Lepidoptera mimicking other Insects Mimicry among Beetles Beetles mimicking other Insects Insects mimicking Species of other Orders Cases of Mimicry among the Vertebrata Mimicry among Snakes Mimicry among Birds Mimicry among Mammals Objections to Mr. Bates' Theory of Mimicry Mimicry by Female Insects only Cause of the dull Colours of Female Birds Use of the gaudy Colours of many Caterpillars Summary General deductions as to Colour in Nature Conclusion IV.--_The Malayan Papilionidae, or Swallow-tailed Butterflies, as illustrative of the Theory of Natural Selection._ Pp. 130-200 Special value of the Diurnal Lepidoptera for inquiries of this Nature Question of the rank of the Papilionidae Distribution of the Papilionidae Definition of the word Species Laws and Modes of Variation Simple Variability Polymorphism or Dimorphism Local form or variety Co-existing Variety Race or Subspecies Species Variation as specially influenced by Locality Local Variation of Size Local Variation of Form Local Variations of Colour Remarks on the facts of Local Variation Mimicry Concluding Remarks on Variation in Lepidoptera Arrangement and Geographical Distribution of the Malayan Papilionidae Arrangement Geographical Distribution Range of the Groups of Malayan Papilionidae Remarkable peculiarities of the island of Celebes Concluding Remarks V.--_On Instinct in Man and Animals._ Pp. 201-210