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CONTENTS.

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CHAPTER I.

VARIATION UNDER DOMESTICATION.

Causes of Variability—Effects 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

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

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CHAPTER V.

LAWS OF VARIATION.

Effects of changed conditions—Use and disuse, combined with

natural selection; organs of flight and of vision-Acclimatisa-

CHAPTER VIII.

INSTINCT.

Instincts comparable with habits, but different in their origin,

Instincts graduated-Aphides and ants—Instincts variable-
Domestic instincts, their origin — Natural instincts of the
cuckoo, Molothrus, ostrich, and parasitic bees-Slave-making
ants-Hive-bee, its cell-making instinct-Changes of instinct
and structure not necessarily simultaneous-Difficulties of the
theory of the Natural Selection of instincts-Neuter or sterile
insects--Summary .

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