ust
therefore have reached the island either _since_ then, in which case
they certainly must have passed through the air for long distances, or
at the time of the union. But the Miocene and Eocene periods were
certainly warm, and these alpine plants could hardly have migrated over
tropical forest lands, while it is very improbable that if they had been
isolated at so remote a period, exposed to such distinct climatal and
organic environments as in Madagascar and Abyssinia, they would have in
both places retained their specific characters unchanged. The
presumption is, therefore, that they are comparatively _recent_
immigrants, and if so must have passed across the sea from mountain to
mountain, for the richness and speciality of the Madagascar forest
vegetation render it certain that no recent glacial epoch has seriously
affected that island.

Hoping that you are in good health, and wishing you the compliments of
the season, I remain yours very faithfully,

ALFRED R. WALLACE.

* * * * *

_Down, Beckenham, Kent. January 2, 1881._

My dear Wallace,--The case which you give is a very striking one, and I
had overlooked it in _Nature._[115] But I remain as great a heretic as
ever. Any supposition seems to me more probable than that the seeds of
plants should have been blown from the mountains of Abyssinia or other
central mountains of Africa to the mountains of Madagascar. It seems to
me almost infinitely more probable that Madagascar extended far to the
south during the Glacial period, and that the southern hemisphere was,
according to Croll, then more temperate; and that the whole of Africa
was then peopled with some temperate forms, which crossed chiefly by
agency of birds and sea-currents; and some few by the wind from the
shores of Africa to Madagascar, subsequently ascending to the mountains.

How lamentable it is that two men should take such widely different
views, with the same facts before them; but this seems to be almost
regularly our case, and much do I regret it.

I am fairly well, but always feel half dead with fatigue. I heard but an
indifferent account of your health some time ago, but trust that you are
now somewhat stronger.--Believe me, my dear Wallace, yours very
sincerely,

CH. DARWIN.

* * * * *

_Down, Beckenham, Kent. January 7, 1881._

My dear Wallace,--You know from Miss Buckley that, with her assistance,
I drew up a memor