I have
therefore been able to appreciate the value of your evidence on these
points. What progress Palaeontology has made during the last 20 years!
But if it advances at the same rate in the future, our views on the
migration and birthplace of the various groups will, I fear, be greatly
altered. I cannot feel quite easy about the Glacial period and the
extinction of large mammals, but I much hope that you are right. I think
you will have to modify your belief about the difficulty of dispersal of
land molluscs; I was interrupted when beginning to experimentise on the
just-hatched young adhering to the feet of ground-roosting birds. I
differ on one other point, viz. in the belief that there must have
existed a Tertiary Antarctic continent, from which various forms
radiated to the southern extremities of our present continents. But I
could go on scribbling for ever. You have written, as I believe, a grand
and memorable work, which will last for years as the foundation for all
future treatises on Geographical Distribution,--My dear Wallace, yours
very sincerely,
CHARLES DARWIN.
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