If, on the other hand, we
view "Persistent Types" in relation to that hypothesis which supposes the
species living at any time to be the result of the gradual modification of
pre-existing species, a hypothesis which, though unproven, and sadly
damaged by some of its supporters, is yet the only one to which physiology
lends any countenance; their existence would seem to show that the amount
of modification which living beings have undergone during geological time
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.
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