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Show CONTENTS. INTRODUOTION, Page g CHAPTER I. VARIATION UNDER DOMESTICATION. Oauses of Variability- Effects of Habit-Correlation of Growth-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-Principle of Selection anciently followed, its Effects-Methodical and Unconsciou~ Selection-Unknown 01·igin of our Domestic Productions-Circumstances favourable to Man's power of Selection, • 14 CHAPTER II. VARIATION UNDER NATURE. Variability-Individual difference£~-Doubtful species-Wide ranging, much diffused, and common species vary most-Species of the larger genera in any country vary more 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, • 46 CHAPTER III. STRUGGLE FOR EXISTENCE. Bears on natural selection-The term used in a wide sense-Geometrical powers of increase-Rapid increase of naturalised animals and plants-Nature of the checks to increase-Competition universal-Effects of climate-Protection from the number of individuals-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 important of all relations, . 60 CHAPTER IV. NATURAL SELEOTIO:N , Natural Selection-its power compared with man's selectiqn-its power on characters of trifiing importance-its power at all a~es and. qn both sexes-Sexual_Selectlon- |