X CONTENTS 



PAGE 



affinities of extinct species to each other and to living species — 

 On the state of development of ancient forms — On the succession 

 of the same types within the same areas — Summary of preceding 

 and present chapter 296 



CHAPTER XII 



GEOGRAPHICAL DISTRIBUTION 



Present distribution cannot be accounted for by differences in physical 

 conditions — Importance of barriers — Affinity of the productions 

 of the same continent — Centres of creation — Means of dispersal 

 by changes of climate and of the level of the land, and by occa- 

 sional means — Dispersal during the Glacial period — Alternate 

 Glacial periods in the north and south 323 



CHAPTER XIII 



GEOGRAPHICAL DISTRIBUTION — Continued 



Distribution of fresh-water productions — On the inhabitants of oceanic 

 islands — Absence of Batrachians and of terrestrial Mammals — On 

 the relation of the inhabitants of islands to those of the nearest 

 mainland — On colonization from the nearest source with subse- 

 quent modification — Summary of the last and present chapter . 3S1 



CHAPTER XIV 



MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY 



EMBRYOLOGY RUDIMENTARY ORGANS 



Classification, groups subordinate to groups — ^Natural system — Rules 

 and difiiculties in classification, explained on the theory of descent 

 with modification — Classification of varieties — Descent always used 

 in classification — Analogical or adaptive characters — Affinities, gen- 

 eral, complex and radiating — Extinction separates and defines 

 groups — Morphology, between members of the same class, between 

 parts of the same individual — Embryology, laws of, explained by 

 variations not supervening at an early age, and being inherited 

 at a corresponding age — Rudimentary organs, their origin ex- 

 plained — Summary 371 



CHAPTER XV 



RECAPITULATION AND CONCLUSION 



Recapitulation of the objections to the theory of Natural Selection — 

 Recapitulation of the general and special circumstances in its favor 

 — Causes of the general belief in the immutability of species — 

 How far the theory of Natural Selection may be extended — 

 Effects of its adoption on the study of Natural History — Con- 

 cluding remarks 413 



Glossary of Scientific Terms 441 



Index 459 



