ty days. Now, I myself observed that several of these bits of
broken trees, torn down by floods in heavy storm time from the banks of
Spanish or Portuguese rivers, reached my island in eight or ten days
after leaving the mainland, and sometimes contained eggs of small
land-snails. But as very long 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 opportunity to adapt
itself perfectly by natural selection to the new conditions. The
consequence was, 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 Europe 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 in the egg on the feet of stray waders
or water-birds, which gradually peopled the island after the Glacial
epoch.

Birds and all other 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 bullfinch was driven out to sea by a violent storm, and perched
at last on a bush at Fayal. I wondered at first whether he would effect
a settlement. But at that time no seeds or fruits fit for bullfinches
to eat existed on the islands. Still, as it turned out, this particular
bullfinch happened to have in his crop several undigested seeds of
European plants exactly suited to the bullfinch taste; so when he died
on the spot, these seeds, germinating abundantly, gave rise to a whole
valleyful of appropriate plants for bullfinches to feed upon. Now,
however, there was no bullfinch to eat them. For a long time, indeed,
no other bullfinches arrived at my archipelago. Once, to be sure, a few
hundred years later, a single cock bird did reach the island alone,
much exhausted with his journey, and managed to pick up a living for
himself off the seeds introduced by his unhappy predecessor. But as he
had no mate, he died at last, as