he introduction of New
Species._ Pp. 1-25

Geographical distribution dependent on Geologic Changes

A Law deduced from well-known Geographical and Geological facts

The form of a true system of Classification determined by this Law

Geographical Distribution of Organisms

Geological Distribution of the forms of Life

High Organization of very ancient Animals consistent with this Law

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 o