CONTENTS xiii 



CHAPTER XVI 



PAGE 



The continuity of life The conception of species The principles of 



taxonomy The taxonomic evidence of organic evolution . .221 



CHAPTER XVII "T6" 



Connecting links Homology and analogy Convergent evolution 



Change of function Vestigial structures Reversion . . . 232 



CHAPTER XVIII I I 



Ontogeny The recapitulation hypothesis Interpretation of the onto- 

 genetic record Palingenetic and csenogenetic characters 



CHAPTER XIX 



The stratified rocks Geological periods The age of the habitable earth 

 The geological record The succession of the great vertebrate 

 groups 282 



CHAPTER XX 



Fossil pedigrees Ancestry of birds, horses, elephants and whales . 305 



CHAPTER XXI ' 



Geographical distribution Areas of distribution Barriers to migra- 

 tionMeans of dispersal Changes in the physical conditions of 

 the earth's surface The evidence afforded by the study of geogra- 

 phical distribution with regard to the theory of organic evolution . 319 



CHAPTER XXII 



Adaptation to environment in animals Deep sea animals The coloura- 

 tion of animals Protective and aggressive resemblances Warning 

 colours Mimicry Epigamic ornamentation ..... 334 



CHAPTER XXIII 



Adaptation to the environment in plants Alpine plants, desert plants 

 and lianes The modification of flowers in relation to insect- 

 fertilization ... 350 



PART V. FACTORS OF ORGANIC EVOLUTION 



CHAPTER XXIV 

 Views of Buff on, Erasmus Darwin and Lamarck 365 



CHAPTER XXV 



Robert Chambers and the "Vestiges of Creation" Natural selection 



The views of Charles Darwin and Alfred Russel Wallace . . 383 



