CONTENTS 

 Volume I 



PAGE 



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 vari- 

 eties — 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, an- 

 ciently followed, their effects — Methodical and unconscious selec- 

 tion — Unknown origin of our domestic productions — Circum- 

 stances favorable 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 33 



CHAPTER III 



STRUGGLE FOR EXISTENCE 



Its bearing on natural selection — The term used in a wide sense — Geo- 

 metrical ratio of increase — Rapid increase of naturalized animals 

 and plants — Nature of the checks to increase — Competition uni- 

 versal — Effects of climate — Protection from the number of indi- 

 viduals^ — Complex relations of all animals and plants throughout 

 nature — Struggle for life most severe between individuals and 

 varieties of the same species: often severe between species of the 

 same genus — The Relation of organism to organism the most im- 

 portant of all relations _ 48 



