CONTENTS. 

 \ 



ADDITIONS AND CORRECTIONS, TO THE SIXTH EDITION . . Page xi 

 HISTORICAL SKETCH . . . . . . . . . . . . xiii 



INTRODUCTION .. .. .. .. .. -. .. .. 1 



CHAPTER I. 



VARIATION UNDER DOMESTICATION. 



Causes of Variability Effects of Habit and the use or disuse of Parts 

 Correlated Variation Inheritance Character of Domestic Varieties 

 Difficulty of distinguishing between Varieties and Species Origin of 

 domestic varieties from one or more species Domestic Pigeons, their 

 Differences and Origin Principles of Selection, anciently followed, their 

 Effects Methodical and Unconscious Selection Unknown Origin of our 

 Domestic Productions Circumstances favourable to Man's power of 

 Selection 5 



CHAPTER II. 



VARIATION UNDER NATURE. 



Variability Individual differences Doubtful species Wide ranging, much 

 diffused, and common species, vary most Species of the larger genera in 

 each country vary more frequently than the species of the smaller genera 

 Many of the species of the larger genera resemble varieties in being 

 very closely, but unequally, related to each other, and in having restricted 

 ranges 30 



CHAPTER in. 



STRUGGLE FOR EXISTENCE. 



Its bearing on natural selection The term used in a wide sense Geometrical 

 ratio of increase Rapid increase of naturalised animals and plants 

 Nature of the checks to increase Competition universal Effects of 



