becoming extinct there under stress of competition with higher forms,
it now survives only in these two widely separated insular areas.

It was an endless amusement to me during those long centuries, while I
devoted myself entirely to the task of watching my fauna and flora
develop itself, to look out from day to day for any chance arrival by
wind or waves, and to follow the course of its subsequent vicissitudes
and evolution. In a great many cases, especially at first, the
new-comer found no niche ready for it in the established order of
things on the islands, and was fain at last, after a hard struggle, to
retire for ever from the unequal contest. But often enough, too, he
made a gallant fight for it, and, adapting himself rapidly to his new
environment, changed his form and habits with surprising facility. For
natural selection, I found, is a hard schoolmaster. If you happen to
fit your place in the world, you live and thrive, but if you don't
happen to fit it, to the wall with you without quarter. Thus sometimes
I would see a small canary beetle quickly take to new food and new
modes of life on my islands under my very eyes, so that in a century or
so I judged him myself worthy of the distinction of a separate species;
while in another case, I remember, a south European weevil evolved
before long into something so wholly different from his former self
that a systematic entomologist would have been forced to enrol him in a
distinct genus. I often wish now that I had kept a regular collection
of all the intermediate forms, to present as an illustrative series to
one of your human museums; but in those days, of course, we none of us
imagined anybody but ourselves would ever take an interest in these
problems of the development of life, and we let the chance slide till
it was too late to recover it.

Naturally, during all these ages changes of other sorts were going on