292 THE ARU ISLANDS. [chap, xxxiii. 



implies a former connexion of the adjacent lands ; but if 

 this evidence is wanting, or if there is reason to suspect a 

 rising of the land, then the shallow sea may he the result 

 of that rising, and may indicate that the two countries will 

 be joined at some future time, hut not that they have 

 previously been so. The nature of the animals and plants 

 inhabiting these countries wiU, however, almost always 

 enable us to determine this question. Mr. Darwin lias 

 shown us how we may determine in almost every case, 

 whether an island has ever been connected with a con- 

 tinent or larger land, by the presence or absence of terres- 

 trial Mammalia and reptiles. What he terms " oceanic 

 islands " possess neither of these groups of animals, though 

 they may have a luxuriant vegetation, and a fair number of 

 birds, insects, and land-shells ; and we therefore conclude 

 that they have originated in mid-ocean, and have never 

 been connected with the nearest masses of land. St. 

 Helena, Madeira, and New Zealand are examples of 

 oceanic islands. They possess all other classes of life, 

 because these have means of dispersion over wide spaces 

 of sea, which terrestrial mammals and birds have not, as 

 is fully explained in Sir Charles Lyell's " Principles of 

 Geology," and Mr. Darwin's " Origin of Species." On the 

 other hand, an island may never have been actually con- 

 nected with the adjacent continents or islands, and yet 

 may possess representatives of all classes of animals, 



