INTRODUCTION.
When on board H.M.S. 'Beagle,' as naturalist, I was much struck with
certain facts in the distribution of the inhabitants of South America, and
in the geological relations of the present to the past inhabitants of that
continent. These facts seemed to me to throw some light on the origin of
species—that mystery of mysteries, as it has been called by one of
our greatest philosophers. On my return home, it occurred to me, in 1837,
that something might perhaps be made out on this question by patiently
accumulating and reflecting on all sorts of facts which could possibly
have any bearing