GEOGRAPHICAL DISTRIBUTION 357 



for their transportal. Would the just-hatched young 

 occasionally crawl on and adhere to the feet of birds 

 roosting on the ground, and thus get transported ? It 

 occurred to me that land-shells, when hibernating and 

 having a membranous diaphragm over the mouth of 

 the shell, might be floated in chinks of drifted timber 

 across moderately wide arms of the sea. And I found 

 that several species did in this state withstand un- 

 injured an immersion in sea-water during seven days : 

 one of these shells was the Helix pomatia, and after 

 it had again hibernated I put it in sea-water for twenty 

 days, and it perfectly recovered. As this species has 

 a thick calcareous operculum, I removed it, and when 

 it had formed a new membranous one, I immersed it 

 for fourteen days in sea-water, and it recovered and 

 crawled away : but more experiments are wanted on 

 this head. 



The most striking and important fact for us in regard 

 to the inhabitants of islands, is their affinity to those of 

 the nearest mainland, without being actually the same 

 species. Numerous instances could be given of this 

 fact. I will give only one, that of the Galapagos 

 Archipelago, situated under the equator, between 500 

 and 600 miles from the shores of South America. 

 Here almost every product of the land and water bears 

 the unmistakable stamp of the American continent. 

 There are twenty-six land-birds and twenty-five of 

 these are ranked by Mr. Gould as distinct species, 

 supposed to have been created here ; yet the close 

 affinity of most of these birds to American species in 

 every character, in their habits, gestures, and tones of 

 voice, was manifest. So it is with the other animals, 

 and with nearly all the plants, as shown by Dr. Hooker 

 in his admirable memoir on the Flora of this archi- 

 pelago. The naturalist, looking at the inhabitants of 

 these volcanic islands in the Pacific, distant several 

 hundred miles from the continent, yet feels that he 

 is standing on American land. Why should this be 

 so? why should the species which are supposed to 

 have been created in the Galapagos Archipelago, and 



