CONTENTS. 



CHAPTER IV. 



EVOLUTION AS THE KEY TO DISTRIBUTION. 



Importance of the Doctrine of Evolution— The Origin of New Species— Variation in 

 Animals— The amount of variation in North American Birds — How new species 

 arise from a variable species — Definition and Origin of Genera — Cause of the 

 extinction of Species — The rise and decay of Species and Genera — Discontinuous 

 specific areas, why rare — Discontinuity of the area of Parus palustris— Disconti- 

 nuity of Emberiza schoeniclus — The European and Japanese Jays — Supposed ex- 

 amples of discontinuity among North American Birds— Distribution and antiquity 

 of Families — Discontinuity a proof of antiquity — Concluding Remarks 



Payes 54-69 



CHAPTER V. 



THE POWERS OF DISPERSAL OF ANIMALS AND PLANTS. 



Statement of the general question of Dispersal — The Ocean as a barrier to the dis- 

 persal of Mammals — The dispersal of Birds — The dispersal of Reptiles — The 

 dispersal of Insects — The dispersal of Land Mollusca — Great antiquity of Land- 

 shells — Causes favouring the abundance of Land-shells — The dispersal of Plants 

 — Special adaptability of Seeds for dispersal — Birds as agents in the dispersal of 

 Seeds — Ocean currents as agents in Plant dispersal — Dispersal along mountain- 

 chains — Antiquity of Plants as affecting their distribution . . Pages 70 — 80 



CHAPTER VI. 



GEOGRAPHICAL AND GEOLOGICAL CHANGES : THE PERMANENCE OF CONTINENTS. 



Changes of Land and Sea, their nature and extent — Shore-deposits and stratified 

 rocks — The Movements of Continents — Supposed oceanic formations ; the Origin 

 of Chalk— Fresh-water and Shore-deposits as proving the permanence of Conti- 

 nents — Oceanic Islands as indications of the permanence of Continents and 

 Oceans — General stability of Continents with constant change of form — Effect of 

 Continental Changes on the Distribution of Animals — Changed distribution proved 

 by the extinct animals of different epochs — Summary of evidence for the general 

 permanence of Continents and Oceans ... . . Payes 81 — 102 



CHAPTER VII. 



CHANGES OF CLIMATE WHICH HAVE INFLUENCED THE DISPERSAL OF ORGANISMS : 

 THE GLACIAL EPOCH. 



Proofs of the recent occurrence of a Glacial Epoch — Moraines — Travelled Blocks — 

 Glacial deposits of Scotland: the "Till" — Inferences from the glacial phenomena 

 of Scotland — Glacial phenomena of North America — Effects of the Glacial Epoch 

 on animal life — Warm and cold periods — Palseontological evidence of alternate 

 cold and warm periods — Evidence of interglacial warm periods on the Continent 

 and in North America — Migrations and extinctions of Organisms caused by the 

 Glacial Epoch Payes 103—120 



