he flora of Australia and its
relation to that of New Zealand.

In the more general explanation of the relations of the various northern
and southern floras, I have shown what an important aid to any such
explanation is the theory of repeated changes of climate, not necessarily
of great amount, given in Chapters VIII. and IX.; while the whole
discussion justifies the importance attached to the theory of the general
permanence of continents and oceans, as demonstrated in Chapter VI., since
any rational explanation based upon facts (as opposed to mere unsupported
{530} conjecture) must take such general permanence as a starting-point.
The whole inquiry into the phenomena presented by islands, which forms the
main subject of the present volume has, I think, shown that this theory
does afford a firm foundation for the discussion of questions of
distribution and dispersal; and that by its aid, combined with a clear
perception of the wonderful powers of dispersion and modification in the
organic world when long periods are considered, the most difficult problems
connected with this subject cease to be insoluble.

* * * * *

{531}

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--Investigation of the Facts of Dispersal--of the Means of
Dispersal--of Geographical 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 ch