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CONTENTS.

1.-On the Law which has regulated the introduction of New

Species.

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-Geo-

graphical 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– Rudi-
mentary Organs—Conclusion . . . . . . Pp. 1-25

III.-Mimicry, and other Protective Resemblances among

Animals.

Test of true and false Theories—Importance of the Principle of Utility

--Popular Theories of Colour in Animals-Importance of Conceal-
ment 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
OrdersCases of Mimicry among the Vertebrata--Mimicry among
Snakes—Mimicry among Birds-Mimicry among Mammals—Objec-
tions 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 . . . . . Pp. 45-129

IV.-The Malayan Papilionido, or Swallow-tailed Butterflies,

as illustrative of the Theory of Natural Selection.

Special value of the Diurnal Lepidoptera for inquiries of this Nature-

Question of the rank of the Papilionidae—Distribution of the Papi-
lionidæ-Definition of the word Species—Laws and Modes of Varia-
tion - 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-Re-

marks on the facts of Local Variation - Mimicry — Concluding

Remarks on Variation in Lepidoptera-Arrangement-Geographical

Distribution - Remarkable peculiarities of the island of Celebes-

Concluding Remarks . . . . . . . Pp. 130—200

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ON THE LAW WHICH HAS REGULATED THE INTRODUCTION OF NEW SPECIES. *

: Geographical Distribution dependent on Geologic

Changes. EVERY naturalist who has directed his attention to the subject of the geographical distribution of animals and plants, must have been interested in the singular facts which it presents. Many of these facts are quite different from what would have been anticipated, and have hitherto been considered as highly curious, but quite inexplicable. None of the explanations attempted from the time of Linnæus are now considered at all satisfactory; none of them have given a cause sufficient to account for the facts known at the time, or comprehensive enough to include all the new facts which have since been, and are daily being added. Of late years, however, a great light has been thrown upon the subject by geological investigations, which have shown that the present state of the earth and of the organisms now

* Written at Sarawak in February, 1855, and published in the “Annals and Magazine of Natural History," September, 1855.

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