Contents

Introduction

Chapter 1: Variation under Domestication

Causes of Variability

Effects of Habit and of 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

Breeds of the Domestic Pigeon, their Differences and Origin

Principles of Selection anciently followed, and their Effects

Unconscious Selection

Circumstances favourable to Man's Power of Selection

Chapter 2: Variation under Nature

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 included within the Larger Genera resemble Varieties in being very closely, but unequally, related to each other, and in having restricted ranges

Summary

Chapter 3: Struggle for Existence

The Term, Struggle for Existence, used in a large sense

Geometrical Ratio of Increase

Nature of the Checks to Increase

Complex Relations of all Animals and Plants to each other in the Struggle for Existence

Complex Relations of all Animals and Plants to each other in the Struggle for Existence (cont)

Struggle for Life most severe between Individuals and Varieties of the same Species

Chapter 4: Natural Selection; or Survival of The Fittest

Sexual Selection

Illustrations of the Action of Natural Selection, or the Survival of the Fittest

On the Intercrossing of Individuals

Circumstances favourable for the production of new forms through Natural Selection

Extinction caused by Natural Selection

Divergence of Character

The Probable Effects of the Action of Natural Selection through Divergence of Character and Extinction, on the Descendants of a Common Ancestor

On the Degree to which Organisation tends to advance

Convergence of Character

Summary of Chapter