THE LIFE OF ISLANDS. 223 



The lizards give us no trouble in accounting for 

 their presence on these islands. Their American con- 

 nections point to an origin from that continent ; and 

 that they are importations originally conveyed, them- 

 selves or their eggs, on driftwood or even by swimming 

 to the Galapagos, is a theory of very feasible nature. 

 The snakes are more unusual tenants of oceanic islands. 

 Two species occur on the Galapagos ; but both are 

 near relations of South American serpents, and one, it 

 is added, is scarcely to be distinguished from a Chilian 

 species. Serpents are animals which are very tenacious 

 of life, and their powers of swimming are also, on the 

 whole, of a very well-developed kind. 



" On one occasion," Dr. Wallace relates, " a boa- 

 constrictor swam from South America to the island of 

 St. Vincent, which is distant 200 miles, at the very 

 least, from the continent." So that, as regards the 

 snakes of the Galapagos, there is even less difficulty 

 than is met with in the case of the lizards. Carried 

 on floating trees, or even swimming across the inter- 

 vening ocean, into which a river-flood may have swept 

 them, snakes may readily reach lands far distant from 

 their native habitats. 



But that which is most interesting in connection 

 with the Galapagos reptiles is the presence on their 

 islands of huge tortoises. These huge reptiles must be 

 familiar to visitors to the London Zoological Gardens. 

 They represent enormously enlarged editions, as it 

 were, of the familiar tortoises of every-day life ; so 

 large, indeed, that a man might easily sit on the back 

 of one and be conveyed by the animal without the 

 latter being aware of the burden it was carrying. 



Big tortoises are not common animals. We find 

 them also in the Mascarene Islands, which are associated 



