12 AfV ISLANDS. 



small land-snails. But as very \ox\^ periods often 

 passed without a single new species being introduced 

 into the group, any kind that once managed to establish 

 itself on any of the islands usually remained for ages 

 undisturbed by new arrivals, and so had plenty of oppor- 

 tunity to adapt itself perfectly by natural selection to 

 the new conditions. The consequence w^as, that out of 

 some seventy land-snails now known in the islands, 

 thirty-two had assumed distinct specific features before 

 the advent of man, while thirty-seven (many of which, I 

 think, I never noticed till the introduction of cultivated 

 plants) are common to my group with l^uropo or with 

 the other Atlantic islands. Most of these, I believe, 

 came in with man and his disconcerting agriculture. 



As to the pond and river snails, so far as I could 

 observe, they mostly reached us later, being conveyed 

 ill the egg on the feet of stray waders or water-birds, 

 which gradually peopled the island after the Glacial epoch, 

 Birds and all otlier flying creatures are now very 

 abundant in all the islands ; but I could tell you some 

 curious and interesting facts, too, as to the mode of their 

 arrival and the vicissitudes of their settlement. For 

 example, during the age of the Forest Beds in Europe, 

 a stray bulUinch was driven out to sea by a violent storm, 

 and perched at last on a bush at Fayal. I wondered a; 

 first whether he w^ould effect a settlement. But at tha; 

 time no seeds or fruits fit for bulltinches to eat existed 

 on the islands. Still, as it turned out, this particular 

 bullfinch happened to have in his crop several undigestei 

 seeds of European plants exactly suited to the bulllincl; 

 taste; so when he died on the spot, these seeds, 



