Chapter I: Preface

Of the six chapters which constitute this concluding volume of G. J. Romanes' _Darwin, and after Darwin_, three, the first two and the last, were in type at the time of his death. I have not considered myself at liberty to make any alterations of moment in these chapters. For the selection and arrangement of all that is contained in the other three chapters I am wholly responsible.

Two long controversial Appendices have been omitted. Those marked A and B remain in accordance with the author's expressed injunctions. In a third, marked C, a few passages from the author's note-books or MSS. have been printed.

The portrait of the Rev. J. Gulick, which forms the frontispiece, was prepared for this volume before the author's death. Mr. Gulick's chief contributions to the theory of physiological selection are to be found in the Linnean Society's _Journal_ (_Zoology_, vols. xx and xxiii), and in four letters to _Nature_ (vol. xli. p. 536; vol. xlii. pp. 28 and 369; and vol. xliv. p. 29).

I have to thank Mr. Francis Galton, D.C.L., F.R.S. and Mr. F. Howard Collins for valuable assistance generously rendered for the sake of one whom all who knew him held dear. For he was, if I may echo the words of Huxley, "a friend endeared to me, as to so many others, by his kindly nature, and justly valued by all his colleagues for his powers of investigation and his zeal for the advancement of science."

C. LLOYD MORGAN.

BRISTOL, _May 1897_.

CONTENTS

CHAPTER I. ISOLATION 1

CHAPTER II. ISOLATION (_continued_) 28

CHAPTER III. PHYSIOLOGICAL SELECTION 41

CHAPTER IV. EVIDENCES OF PHYSIOLOGICAL SELECTION 62

CHAPTER V. FURTHER EVIDENCES OF PHYSIOLOGICAL SELECTION 81

CHAPTER VI. A BRIEF HISTORY OF ISOLATION AS A FACTOR IN ORGANIC EVOLUTION 101

GENERAL CONCLUSIONS 144

APPENDIX A. MR. GULICK'S CRITICISM OF MR. WALLACE'S VIEWS ON PHYSIOLOGICAL SELECTION 151

APPENDIX B. AN EXAMINATION BY MR. FLETCHER MOULTON OF MR. WALLACE'S CALCULATION TOUCHING THE POSSIBILITY OF PHYSIOLOGICAL SELECTION EVER ACTING ALONE 157

APPENDIX C. SOME EXTRACTS FROM THE AUTHOR'S NOTE-BOOKS 169

_ISOLATION_