CHAPTER XXIV 



SUMMARY AND CONCLUSION 



The Present Volume is the Development and Application of a Theory — 

 Statement of the Biological and Physical Causes of Dispersal — Investi- 

 gation of the Facts of Dispersal — of the Means of Dispersal— of Geo- 

 graphical Changes Affecting Dispersal — of Climatal Changes Affecting 

 Dispersal — The Glacial Epoch and its Causes — Alleged Ancient Glacial 

 Epochs — Warm Polar Climates and their Causes — Conclusions as to 

 Geological Climates — How far Different from those of Mr. Croll — 

 Supposed Limitations of Geological Time — Time Amply Sufficient both 

 for Geological and Biological Development — Insular Faunas and Floras 

 — The North Atlantic Islands — The Galapagos — St. Helena and the 

 Sandwich Islands — Great Britain as a Recent Continental Island — 

 Borneo and Java — Japan and Formosa — Madagascar as an Ancient 

 Continental Island — Celebes and New Zealand as Anomalous Islands — 

 The Flora of New Zealand and its Origin — The European Element in 

 the South Temperate Floras — Concluding Remarks. 



The present volume has gone over a very wide field both 

 of facts and theories, and it will be well to recall these to 

 the reader's attention and point out their connection with 

 each other, in a concluding chapter, I hope to be able to 

 show that, although at first sight somewhat fragmentary 

 and disconnected, this work is really the development of a 

 clear and definite theory, and its application to the solution 

 of a number of biological problems. That theory is, 

 briefly, that the distribution of the various species and 

 groups of living things over the earth's surface, and their 

 aggregation in definite assemblages in certain areas, is the 



