CHAP. XIII THE GALAPAGOS ISLANDS 291 



perate or alpine affinities of many of the plants, and even 

 cf some of the birds. The relation between the migratory 

 habits of the birds and the amount of difference from 

 continental types is strikingly accordant with the fact that 

 it is almost exclusively migratory birds that annually reach 

 the Azores and Bermuda ; while the corresponding fact 

 that the seeds of those plants, which are common to the 

 Galapagos and the adjacent continent, have all — as Sir 

 Joseph Hooker states — some special means of dispersal, is 

 equally intelligible. The reason wdiy the Galapagos pos- 

 sess four times as many peculiar species of plants as the 

 Azores is clearly a result of the less constant introduction 

 of seeds, owing to the absence of storms ; the greater 

 antiquity of the group, allowing more time for specific 

 change ; and the influence of cold epochs and of alterations 

 of sea and land, in bringing somewhat different sets of 

 plants at different times within the influence of such 

 modified winds and currents as might convey them to the 

 islands. 



On the whole, then, we have no difficulty in explaining 

 the probable origin of the flora and fauna of the Galapagos, 

 by means of the illustrative facts and general principles 

 already adduced. 



