116 DARWINISM STATED BY DARWIN HIMSELF. 



of such prodigious geographical revolutions within the 

 recent period as are necessary on the view advanced by 

 Forbes and admitted by his followers. The nature and 

 relative proportions of the inhabitants of oceanic islands 

 are likewise opposed to the belief of their former con- 

 tinuity with continents. Nor does the almost universally 

 volcanic composition of such islands favor the admission 

 that they are the wrecks of sunken continents ; if they 

 had originally existed as continental mountain-ranges, 

 some at least of the islands would have been formed, like 

 other mountain-summits, of granite, metamorphic schists, 

 old fossiliferous and other rocks, instead of consisting of 

 mere piles of volcanic matter. 



MEANS OF DISPERSAL. 



p Living birds can hardly fail to be highly 



effective agents in the transportation of seeds. 

 I could give many facts showing how frequently birds of 

 many kinds are blown by gales to vast distances across 

 the ocean. We may safely assume that under such cir- 

 cumstances their rate of flight would often be thirty-five 

 miles an hour ; and some authors have given a far higher 

 estimate. I have never seen an instance of nutritious 

 seeds passing through the intestines of a bird ; but hard 

 seeds of fruit pass uninjured through even the digestive 

 organs of a turkey. In the course of two months I 

 picked up in my garden twelve kinds of seeds out of the 

 excrement of small birds, and these seemed perfect, and 

 some of them, which were tried, germinated. But the 

 following fact is more important : the crops of birds do 

 not secrete gastric juice, and do not, as I know by trial, 

 injure in the least the germination of seeds ; now, after 

 a bird has found and devoured a large supply of food, it 



