CONTENTS. 



Additions and Corrections, to the Sixth Edition . Page Ix 



Historical Sketch xiii 



Introduction 1 



CHAPTER I. 



variation under domestication. 



Causes of Variability — ^BfEects of Habit and the use or disuse of 

 Parts — Correlated Variation — Inheritance — Character of Do- 

 mestic 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 7 



CHAPTER II. 



VARIATION UNDER NATURE. 



Variability — Individual differences — Doubtful species — Wide rang- 

 ing, 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 51 



V 



