4 CONTENTS 



CHAPTER XI 



ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS 



On the slow and successive appearance of new species — On their different 

 rates of change — Species once lost do not reappear — Groups of species 

 follow the same general rules in their appearance and disappearance as 

 do single species — On Extinction — On simultaneous changes in the 

 forms of life throughout the world — On the 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 cliapters . . . .96 



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 occasional means — 

 Dispersal during the Glacial period — Alternate Glacial periods in the 

 North and South 137 



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 subsequent moditication 

 — Summary of the last and present chapters - . . . . .130 



