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Show 498 ISLAND LIFE. (PART 1 f. d. . f questions of distribution a firm .c1 ouncl a t1' 0n £° r the lSC.U SSlO.n 0 b' d with a clear per- . 1 d th t by Its aid, com me and dispersa ; an a 1 f dispersion and modification . f th wonderfu powers o c· eptbho n o ni.c e wor ld wh e. n lonC/' periods are considered, the most o Idnif ficeu lot rgpar oblems connec t e d with this subject cease to be insoluble. CHAPTER XXIV. SUMMARY AND CONCLUSION. The present volume is the development and application of a theory-Statement of the Biological and Physical causes of dispers al- Investigation of the facts of dispersal·-of the means of dispersal-of geographical changes affecting dispersal-of climatal changes affecting dispersalThe glacial epoch and its causes-Alleged ancient glaeial epochsWarm polar climates and their causes-Conclusions as to geologieal climates-How far different from those of Mr. Croll-Supposed limitations of geological time-Time amply sufficient both for geological anrl biological development-Insular faunas and floras-The North Atlantic Islands-'l'he 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-Tho European element in the South Temperate FlorasConcluding Hemarks. 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 distri~ bution 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 direct result and outcome of a complex set of causes, which may be grouped as "biological" and u physical." The biological causes are mainly of two K K 2 |
