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

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.