Vlll CONTENTS. 



CHAPTER X. fAGE 



THE OLDEST AIR-BREATHERS . . . . . . 257 



CHAPTER XI. 

 MARKINGS, FOOTPRINTS, AND FUCOIDS 311 



CHAPTER XII. 

 PRE-DETERMINATION IN NATURE 329 



CHAPTER XIII. 

 THE GREAT ICE AGE 345 



CHAPTER XIV. 

 CAUSES OF CLIMATAL CHANGE 383 



CHAPTER XV. 



THE DISTRIBUTION OF ANIMALS AND PLANTS AS RELATED TO 



GEOGRAPHICAL AND GEOLOGICAL CHANGES . . .401 



CHAPTER XVI. 

 ALPINE AND ARCTIC PLANTS IN CONNECTION WITH GEOLOGICAL 



HISTORY 425 



CHAPTER XVII. 

 EARLY MAN 459 



CHAPTER XVIII. 

 MAN IN NATURE 481 



