xiv CONTENTS 



CHAPTER XXVI 



PAIJB 



Selection not confined to the organic world Illustrations of the action 

 of natural selection in the struggle for existence Degeneration 

 Flightless birds Extermination of the Morioris Sedentary 

 animals Parasites Co-operation of natural selection and the 

 so-called Lamarckian factors of evolution The influence of 

 internal secretions upon growth Increase in size beyond the 

 limits of utility 395 



CHAPTER XXVII 



Artificial selection Continuous and single selection The mutation 

 theory of the origin of species Mutual adaptation Unit 

 characters Isolation Physiological selection Non-adaptive 

 characters The evolution of man 410 



INDEX . 429 



