of the plants of Scandinavia; showing
the high probability of there having been secular periods alternately
wet and dry; and of the important part which they have played in
distribution.

I wrote to Forel, who is always at work on ants, and told him of your
views about the dispersal of the blind Coleoptera, and asked him to
observe.

I spoke to Hooker about your book, and feel sure that he would like
nothing better than to consider the distribution of plants in relation
to your views; but he seemed to doubt whether he should ever have time.

And now I have done my jottings, and once again congratulate you on
having brought out so grand a work. I have been a little disappointed at
the review in _Nature_[111]--My dear Wallace, yours sincerely,

CHARLES DARWIN.

* * * * *

_Rose Hill, Dorking. July 23, 1876._

My dear Darwin,--I should have replied sooner to your last kind and
interesting letters, but they reached me in the midst of my packing
previous to removal here, and I have only just now got my books and
papers in a get-at-able state.

And first, many thanks for your close observation in detecting the two
absurd mistakes in the tabular headings.

As to the former greater distinction of the North and South American
faunas, I think I am right. The Edentata, being proved (as I hold) to
have been mere temporary migrants into North America in the
post-Pliocene epoch, form no part of its Tertiary fauna. Yet in South
America they were so enormously developed in the Pliocene epoch that we
know, if there is any such thing as Evolution, etc., that strange
ancestral forms must have preceded them in Miocene times.

Mastodon, on the other hand, represented by one or two species only,
appears to have been a late immigrant into South America from the North.

The immense development of Ungulates (in varied families, genera, and
species) in North America during the whole Tertiary epoch is, however,
the great feature, which assimilates it to Europe and contrasts it with
South America. True camels, hosts of hog-like animals, true
rhinoceroses, and hosts of ancestral horses, all bring North America
much nearer to the Old World than it is now. Even the horse, represented
in all South America by Equus only, was probably a temporary immigrant
from the North.

As to extending too far the principle (yours) of the necessity of
comparatively large areas for the development of varied faunas, I may