Evolution and Adaptation
The Project Gutenberg eBook, Evolution and Adaptation, by Thomas Hunt Morgan
The cover image was created by the transcriber and is placed in the public domain.
EVOLUTION
AND ADAPTATION
THOMAS HUNT MORGAN, Ph.D.
New York
THE MACMILLAN COMPANY
LONDON: MACMILLAN & CO., Ltd.
1908
All rights reserved
Copyright, 1903,
By THE MACMILLAN COMPANY.
Thomas Hunt Morgan
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EVOLUTION AND ADAPTATION
PREFACE
CONTENTS
Structural Adaptations
Adjustments of the Individual to Changes in the Environment
Adaptations for the Good of the Species
Organs of Little Use to the Individual
Changes in the Organism that are of No Use to the Individual or to the Race
Comparison with Inorganic Phenomena
Evidence in Favor of the Transmutation Theory
THE GEOLOGICAL EVIDENCE
EVIDENCE FROM DIRECT OBSERVATION AND EXPERIMENT
MODERN CRITICISM OF THE THEORY OF EVOLUTION
Conclusions
Variation and Competition in Nature
The Theory of Natural Selection
Sterility between Species
Weismann’s Germinal Selection
General Criticism of the Theory of Sexual Selection
Darwin’s Hypothesis of Pangenesis
The Neo-Lamarckian School
Continuous Variation
Frequency of Different Types of Beech Leaves
Heredity and Continuous Variation
Discontinuous Variation
The Mutation Theory of De Vries
Conclusions
The Effect of External Influences
Responsive Changes in the Organism that adapt it to the New Environment
Nägeli’s Perfecting Principle
Form and Symmetry
Mutual Adaptation of Colonial Forms
Degeneration
Protective Coloration
Length of Life as an Adaptation
Organs of Extreme Perfection
Secondary Sexual Organs as Adaptations
Individual Adjustments as Adaptations
Color Changes as Individual Adaptations
Increase of Organs through Use and Decrease through Disuse
Reactions of the Organism to Poisons, etc.
Regeneration
The Different Kinds of Sexual Individuals
The Determination of Sex
Sex as a Phenomenon of Adaptation
INDEX