22 The Malay Arch],pelago. 



ferent species of animals and plants, whose remains are found 

 in these deposits, prove that corresponding changes did occur 

 in the organic world. 



Taking, therefore, these two series of changes for granted, 

 most of the present peculiarities and anomalies in the distri- 

 bution of species may be directly traced to them. In our 

 own islands, with a very few trifling exceptions, every quadru- 

 ped, bird, reptile, insect, and plant is found also on the adjacent 

 continent. In the small islands of Sardinia and Corsica there 

 are some quadrupeds and insects, and many plants, quite pe- 

 culiar. In Ceylon, more closely connected to India than Brit- 

 ain is to Europe, many animals and plants are different from 

 those found in India, and peculiar to the island. In the Gala- 

 pagos Islands almost every indigenous living thing is peculiar 

 to them, though closely resembling other kinds found in the 

 nearest parts of the American continent. 



Most naturalists now admit that these facts can only be ex- 

 plained by the greater or less lapse of time since the islands 

 were upraised from beneath the ocean, or were separated from 

 the nearest land ; and this will be generally (though not al- 

 ways) indicated by the depth of the intervening sea. The 

 enormous thickness of many marine deposits through wide 

 areas shows that subsidence has often continued (with inter- 

 mitting periods of repose) during epochs of immense duration. 

 The depth of sea produced by such subsidence will therefore 

 generally be a measure of time ; and in like manner the change 

 which organic forms have undergone is a measure of time. 

 When we make proper allowance for the continued introduc- 

 tion of new animals and plants from surrounding countries, 

 by those natural means of dispersal which have been so well 

 explained by Sir Charles Lyell and Mr. Darwin, it is remark- 

 able how closely these two measures correspond. Britain is 

 separated from the continent by a very shallow sea, and only 

 in a very few cases have our animals or j^lants begun to show 

 a difference from the corresponding Continental species. 

 Corsica and Sardinia, divided from Italy by a much deeper 

 sea, present a much greater difference in their organic forms. 

 Cuba, separated from Yucatan by a wider and deeper strait, 

 differs more markedly, so that most of its productions are of 

 distinct and peculiar species ; while Madagascar, divided from 



