CHAPTER XI 



THE CLASSIFICATION OF ISLANDS 



Importance of Islands in the Study of the Distribution of Organisms — 

 Classification of Islands with Reference to Distribution — Continental 

 Islands — Oceanic Islands. 



In the preceding chapters, forming the first part of our 

 work, we have discussed, more or less fully, the general 

 features presented by animal distribution, as well as the 

 various physical and biological changes which have been 

 the most important agents in bringing about the present 

 condition of the organic world. 



We now proceed to apply these principles to the solution 

 of the numerous problems presented by the distribution 

 of animals ; and in order to limit the field of our inquiry, 

 and at the same time to deal only with such facts as may 

 be rendered intelligible and interesting to those readers 

 who have not much acquaintance with the details of 

 natural history, we propose to consider only such phenom- 

 ena as are presented by the islands of the globe. 



Importance of Islands in the Study of the Distribution of 

 Organisms, — Islands possess many advantages for the study 

 of the laws and phenomena of distribution. As compared 

 with continents they have a restricted area and definite 

 boundaries, and in most cases their geographical and 

 biological limits coincide. The number of species and of 

 genera they contain is always much smaller than in the 



