rld!

But we have every reason to believe that the terrestrial productions of the
archipelago would be preserved in an excessively imperfect manner in the
formations which we suppose to be there accumulating. I suspect that not
many of the strictly littoral animals, or of those which lived on naked
submarine rocks, would be embedded; and those embedded in gravel or sand,
would not endure to a distant epoch. Wherever sediment did not accumulate
on the bed of the sea, or where it did not accumulate at a sufficient rate
to protect organic bodies from decay, no remains could be preserved.

I believe that fossiliferous formations could be formed {301} in the
archipelago, of thickness sufficient to last to an age as distant in
futurity as the secondary formations lie in the past, only during periods
of subsidence. These periods of subsidence would be separated from each
other by enormous intervals, during which the area would be either
stationary or rising; whilst rising, each fossiliferous formation would be
destroyed, almost as soon as accumulated, by the incessant coast-action, as
we now see on the shores of South America. During the periods of subsidence
there would probably be much extinction of life; during the periods of
elevation, there would be much variation, but the geological record would
then be least perfect.

It may be doubted whether the duration of any one great period of
subsidence over the whole or part of the archipelago, together with a
contemporaneous accumulation of sediment, would _exceed_ the average
duration of the same specific forms; and these contingencies are
indispensable for the preservation of all the transitional gradations
between any two or more species. If such gradations were not fully
preserved, transitional varieties would merely appear as so many distinct
species. It is, also, probable that each great period of subsidence would
be interrupted by oscillations of level, and that slight climatal changes
would intervene during such lengthy periods; and in these cases the
inhabitants of the archipelago would have to migrate, and no closely
consecutive record of their modifications could be preserved in any one
formation.

Very many of the marine inhabitants of the archipelago now range thousands
of miles beyond its confines; and analogy leads me to believe that it would
be chiefly these far-ranging species which would oftenest produce new
varieties; and the varieties would at first gener