CONTENTS 



CHAPTER I. 



AGE 



ISOLATION i 



CHAPTER II. 

 ISOLATION (continued} ...... 18 



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 



