The Origin of Species

is but very small in relation to the whole series of changes which they
have suffered."

In December, 1859, Dr. Hooker published his "Introduction to the Australian
Flora".  In the first part of this great work he admits the truth of the
descent and modification of species, and supports this doctrine by many
original observations.

The first edition of this work was published on November 24, 1859, and the
second edition on January 7, 1860.



CONTENTS.


INTRODUCTION


CHAPTER I.

VARIATION UNDER DOMESTICATION.

Causes of Variability -- Effects of Habit and 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 -- 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 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.


CHAPTER III.

STRUGGLE FOR EXISTENCE.

Its bearing on natural selection -- The term used in a wide sense --
Geometrical ratio 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.


CHAPTER IV.

NATURAL SELECTION; OR THE SURVIVAL OF THE FITTEST.

Natural Selection -- its power compared with man's selection -- its power
on characters of trifling importance -- its power at all ages and on both
sexes -- Sexual Selection -- On the generality of intercrosses between
individuals of the same species -- Circumstances favourable and
unfavourable to the results of Natural Selection, namely, intercrossing,
isolation, number of individuals -- Slow action -- Extinction caused by
Natural Selection -- Divergence of Character, related to the diversity of
inhabitants of any small area and to naturalisation -- Action of Natural
Selection, through Divergence of Character and Extinction, on the
descendants from a common parent -- Explains the Grouping of all organic
beings -- Advance in organisation -- Low forms preserved -- Convergence of
character -- Indefinite multiplication of species -- Summary.


CHAPTER V.

LAWS OF VARIATION.

Effects of changed conditions -- Use and disuse, combined with natural
selection; organs of flight and of vision -- Acclimatisation -- Correlated
variation -- Compensation and economy of growth -- False correlations --
Multiple, rudimentary, and lowly organised structures variable -- Parts
developed in an unusual manner are highly variable; specific characters
more variable than generic; secondary sexual characters variable -- Species
of the same genus vary in an analogous manner -- Reversions to long-lost
characters -- Summary.


CHAPTER VI.

DIFFICULTIES OF THE THEORY.

Difficulties of the theory of descent with modification -- Absence or
rarity of transitional varieties -- Transitions in habits of life --
Diversified habits in the same species -- Species with habits widely
different from those of their allies -- Organs of extreme perfection --
Modes of transition -- Cases of difficulty -- Natura non facit saltum --