CONTENTS. 



I. Oil the Law which has regulated the introduction of Neiv 

 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 Eudi- 

 mentary Organs Conclusion Pp. 1 25 



II. On the Tendency of Varieties to depart indefinitely from the 

 Original Type. 



Instability of Varieties supposed to prove the permanent distinctness of 

 Species The Struggle for Existence The Law of Population of 

 Species The Abundance or Earity 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 Ori- 

 ginal Species The Partial Eeversion of Domesticated Varieties 

 explained Lamarck's Hypothesis very different from that now 

 advanced Conclusion Pp. 26 44 



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 amongJL/epidoptera 

 Lepicloptera mimicking other Insects Mimicry among Beetles 

 Beetles mimicking other Insacts Insects mimicking Species of other 

 Orders Cases of Mimicry among the Vertebrata Mimicry among 

 Snakes Mimicry among Birds Mimicry among Mammals Objec- 



