10 



ISLAND LIFE. 



[part I. 



dispersal and existing distribution of organisms. The other 

 important theory, or rather corollary from the preceding theory 

 — that of the permanence of oceans and the general stability 

 of continents throughout all geological time, is as yet very 

 imperfectly understood, and seems, in fact, to many persons in 

 the nature of a paradox. The evidence for it, however, appears 

 to me to be conclusive; and it is certainly the most fundamental 

 question in regard to the subject we have to deal with : since, 

 if we once admit that continents and oceans may have changed 

 places over and over again (as many writers maintain), we lose 

 all power of reasoning on the migrations of ancestral forms of 

 life, and are at the mercy of every wild theorist who chooses to 

 imagine the former existence of a now-submerged continent to 

 explain the existing distribution of a group of frogs or a genus 

 of beetles. 



As already shown by the illustrative examples adduced in 

 this chapter, some of the most remarkable and interesting facts 

 in the distribution and affinities of organic forms are presented 

 by islands in relation to each other and to the surrounding 

 continents. The study of the productions of the Galapagos — 

 so peculiar, and yet so decidedly related to the American con- 

 tinent — appear to have had a powerful influence in determining 

 the direction of Mr. Darwin's researches into the origin of 

 species ; and every naturalist who studies them has always been 

 struck by the unexpected relations or singular anomalies which 

 are so often found to characterize the fauna and flora of islands. 

 Yet their full importance in connection with the history of the 

 earth and its inhabitants has hardly yet been recognised ; and 

 it is in order to direct the attention of naturalists to this 

 most promising field of research, that I restrict myself in this 

 volume to an elucidation of some of the problems they present 

 to us. By far the larger part of the islands of the globe are 

 but portions of continents undergoing some of the various 

 changes* to which they are ever subject ; and the correlative 

 statement, that every part of our continents have again and 

 again passed through insular conditions, has not been sufficiently 

 considered, but is, I believe, the statement of a great and most 

 suggestive truth, and one which lies at the foundation of all 



