Science in Arcady | Page 5

of man with his domestic animals, who played havoc at once
with my interesting experiment.
It was quite otherwise with the unobtrusive small deer of life--the snails,
and beetles, and flies, and earthworms--and especially with the winged
things: birds, bats, and butterflies. In the very earliest days of my
islands' existence, indeed, a few stray feathered fowls of the air were

driven ashore here by violent storms, at a time when vegetation had not
yet begun to clothe the naked pumice and volcanic rock; but these, of
course, perished for want of food, as did also a few later arrivals, who
came under stress of weather at the period when only ferns, lichens,
and mosses had as yet obtained a foothold on the young archipelago.
Sea-birds, of course, soon found out our rocks; but as they live off fish
only, they contributed little more than rich beds of guano to the
permanent colonising of the islands. As well as I can remember, the
land-snails were the earliest truly terrestrial casuals that managed to
pick up a stray livelihood in these first colonial days of the archipelago.
They came oftenest in the egg, sometimes clinging to water-logged
leaves cast up by storms, sometimes hidden in the bark of floating
driftwood, and sometimes swimming free on the open ocean. In one
case, as I recall to myself well, a swallow, driven off from the
Portuguese coast, a little before the Glacial period had begun to whiten
the distant mountains of central and northern Europe, fell exhausted at
last upon the shore of Terceira. There were no insects then for the poor
bird to feed upon, so it died of starvation and weariness before the day
was out; but a little earth that clung in a pellet to one of its feet
contained the egg of a land-shell, while the prickly seed of a common
Spanish plant was entangled among the winged feathers by its hooked
awns. The egg hatched out, and became the parent of a large brood of
minute snails, which, outliving the cold spell of the Ice Age, had
developed into a very distinct type in the long period that intervened
before the advent of man in the islands; while the seed sprang up on the
natural manure heap afforded by the swallow's decaying body, and
clinging to the valleys during the Glacial Age on the hill-tops, gave
birth in due season to one of the most markedly indigenous of our
Terceira plants.
Occasionally, too, very minute land-snails would arrive alive on the
island after their long sea-voyage on bits of broken forest-trees--a
circumstance which I would perhaps hesitate to mention in mere human
society were it not that I have been credibly informed your own great
naturalist, Darwin, tried the experiment himself with one of the biggest
European land-molluscs, the great edible Roman snail, and found that it
still lived on in vigorous style after immersion in sea-water for twenty

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