CONTENTS 



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CHAPTER I. 

 Isolation i 



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 loi 



General Conclusions 144 



Appendix A. Mr. Gulick's Criticism of M r. Wallace's 

 Views on Physiological Selection 151 



