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Transcriber's note: A few typographical errors have been corrected: they are listed at the end of the text.
Princeton University
THE LOUIS CLARK VANUXEM FOUNDATION LECTURES FOR 1915 1916
The Louis Clark Vanuxem Foundation of Princeton University
was established in 1912 with a bequest of $25,000 under the will of Louis Clark Vanuxem, of the Class of 1879. By direction of the executors of Mr. Vanuxem's estate, the income of the foundation is to be used for a series of public lectures delivered in Princeton annually, at least one half of which shall be on subjects of current scientific interest. The lectures are to be published and distributed among schools and libraries generally.
The following lectures have already been published or are in press:
1912 13 The Theory of Permutable Functions, by Vito Volterra
1913 14 Lectures delivered in connection with the dedication of the Graduate College of Princeton University by Emile Boutroux, Alois Riehl, A. D. Godley, and Arthur Shipley
1914 15 Romance, by Sir Walter Raleigh
1915 16 A Critique of the Theory of Evolution, by Thomas Hunt Morgan
LOUIS CLARK VANUXEM FOUNDATION
A CRITIQUE
OF THE
THEORY OF EVOLUTION
BY
THOMAS HUNT MORGAN
PROFESSOR OF EXPERIMENTAL ZOOLOGY IN COLUMBIA UNIVERSITY
LECTURES DELIVERED AT PRINCETON UNIVERSITY FEBRUARY 24, MARCH 1, 8, 15, 1916
PRINCETON UNIVERSITY PRESS PRINCETON LONDON: HUMPHREY MILFORD OXFORD UNIVERSITY PRESS 1916
Copyright, 1916, by PRINCETON UNIVERSITY PRESS Published October, 1916
[Illustration]
PREFACE
Occasionally one hears today the statement that we have come to realize that we know nothing about evolution. This point of view is a healthy reaction to the over confident belief that we knew everything about evolution. There are even those rash enough to think that in the last few years we have learned more about evolution than we might have hoped to know a few years ago. A critique therefore not only becomes a criticism of the older evidence but an appreciation of the new evidence.
In the first lecture an attempt is made to put a new valuation on the traditional evidence for evolution. In the second lecture the most recent work on heredity is dealt with, for only characters that are inherited can become a part of the evolutionary process. In the third lecture the physical basis of heredity and the composition of the germ plasm stream are examined in the light of new observations; while in the fourth lecture the thesis is developed that chance variation combined with a property of living things to manifold themselves is the key note of modern evolutionary thought.
T. H. MORGAN
July, 1916
TABLE OF CONTENTS
CHAPTER I A REVALUATION OF THE EVIDENCE ON WHICH THE THEORY OF EVOLUTION WAS BASED
PAGE PREFACE v
1. THREE KINDS OF EVOLUTION 1 7
2. THE EVIDENCE FOR ORGANIC EVOLUTION 7 27 a. The Evidence from Comparative Anatomy 7 14 b. The Evidence from Embryology 14 23 c. The Evidence from Paleontology 24 27
3. THE FOUR GREAT HISTORICAL SPECULATIONS 27 39 a. The Environment 27 31 Geoffroy St. Hilaire b. Use and Disuse 31 34 From Lamarck to Weismann c. The Unfolding Principle 34 36 Nägeli and Bateson d. Natural Selection 36 39 Darwin
CHAPTER II THE BEARING OF MENDEL'S DISCOVERY ON THE ORIGIN OF HEREDITY CHARACTERS
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