CONTENTS 



NATURAL SELECTION 



I. 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 Geographical 

 Distribution of Organisms Geological Distribution of the Forms of 

 Life High Organisation of very ancient Animals consistent with 

 this Law Objections to Forbes's Theory of Polarity Rudimentary 

 Organs Conclusion . . . . Pages 3-19 



II. ON THE TENDENCY OF VARIETIES TO DEPART INDEFINITELY 



FROM THE ORIGINAL TYPE 



Introductory Note Instability of Varieties supposed to prove the per- 

 manent 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 Domesti- 

 cated Varieties explained Lamarck's Hypothesis very different 

 from that now advanced Conclusion .... 20-33 



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 



