X 
CONTENTS 
Variation among birds — Diagrams of bird - variation — Number of 
varying individuals — Variation in the mammalia — Variation in 
internal organs—Variations in the skull — Variations in the habits of 
animals — The variability of plants — Species which vary little — Con¬ 
cluding remarks ..... Pages 41-82 
CHAPTER IV 
VARIATION OF DOMESTICATED ANIMALS AND CULTIVATED 
PLANTS 
The facts of variation and artificial selection — Proofs of the generality of 
variation — Variations of apples and melons — Variations of flowers — 
Variations of domestic animals — Domestic pigeons — Acclimatisation 
— Circumstances favourable to selection by man—Conditions favour¬ 
able to variation — Concluding remarks . . . 83-101 
CHAPTER V 
NATURAL SELECTION BY VARIATION AND SURVIVAL OF THE 
FITTEST 
Effect of struggle for existence under unchanged conditions — The effect 
under change of conditions — Divergence of character — In insects — In 
birds — In mammalia — Divergence leads to a maximum of life in each 
area — Closely allied species inhabit distinct areas — Adaptation to 
conditions at various periods of life—The continued existence of low 
forms of life—Extinction of low types among the higher animals— 
Circumstances favourable to the origin of new species — Probable 
origin of the dippers — The importance of isolation — On the advance 
of organisation by natural selection — Summary of the first five 
chapters ....... 102-125 
CHAPTER VI 
DIFFICULTIES AND OBJECTIONS 
Difficulty as to smallness of variations—As to the right variations occur¬ 
ring when required — The beginnings of important organs — The mam¬ 
mary glands — The eyes of flatfish — Origin of the eye — Useless or 
non-adaptive characters—Recent extension of the region of utility in 
