ecome
partially mingled with them.

I am far from satisfied with what I have scribbled. I conclude that
there must have been a mundane Glacial period, and that the difficulties
are much the same whether we suppose it contemporaneous over the world,
or that longitudinal belts were affected one after the other. For
Heaven's sake forgive me!

LETTER 353. TO H.W. BATES. March 26th [1861].

I have been particularly struck by your remarks on the Glacial period.
(353/1. In his "Contributions to the Insect Fauna of the Amazon Valley,"
"Trans. Entom. Soc." Volume V., page 335 (read November 24th, 1860),
Mr. Bates discusses the migration of species from the equatorial regions
after the Glacial period. He arrives at a result which, he points
out, "is highly interesting as bearing upon the question of how far
extinction is likely to have occurred in equatorial regions during
the time of the Glacial epoch."..."The result is plain, that there
has always (at least throughout immense geological epochs) been an
equatorial fauna rich in endemic species, and that extinction cannot
have prevailed to any extent within a period of time so comparatively
modern as the Glacial epoch in geology." This conclusion does not
support the view expressed in the "Origin of Species" (Edition I.,
chapter XI., page 378) that the refrigeration of the earth extended to
the equatorial regions. (Bates, loc. cit., pages 352, 353.)) You seem
to me to have put the case with admirable clearness and with crushing
force. I am quite staggered with the blow, and do not know what to
think. Of late several facts have turned up leading me to believe more
firmly that the Glacial period did affect the equatorial regions; but I
can make no answer to your argument, and am completely in a cleft
stick. By an odd chance I have only a few days ago been discussing
this subject, in relation to plants, with Dr. Hooker, who believes to a
certain extent, but strongly urged the little apparent extinction in the
equatorial regions. I stated in a letter some days ago to him that the
tropics of S. America seem to have suffered less than the Old World.
There are many perplexing points; temperate plants seem to have migrated
far more than animals. Possibly species may have been formed more
rapidly within tropics than one would have expected. I freely confess
that you have confounded me; but I cannot yet give up my belief that the
Glacial period did to certain extent affect the tropics