ould to the equator they would halt,
and then the confusion would spread back in the line of march from the
far north, and the strongest would struggle forward, etc., etc. (But
I am getting quite poetical in my wriggles). In short, I THINK the
warm-temperates would be exposed very much longer to those causes which
I believe are alone efficient in producing change than the sub-arctic;
but I must think more over this, and have a good wriggle. I cannot quite
agree with your proposition that because the sub-arctic have to travel
twice as far they would be more liable to change. Look at the two
journeys which the arctics have had from N. to S. and S. to N., with no
change, as may be inferred, if my doctrine is correct, from similarity
of arctic species in America and Europe and in the Alps. But I will not
weary you; but I really and truly think your last objection is not so
strong as it looks at first. You never make an objection without doing
me much good. Hurrah! a seed has just germinated after 21 1/2 hours in
owl's stomach. This, according to ornithologists' calculation, would
carry it God knows how many miles; but I think an owl really might go in
storm in this time 400 or 500 miles. Adios.

Owls and hawks have often been seen in mid-Atlantic.

(336/1. An interesting letter, dated November 23rd, 1856, occurs in the
"Life and Letters," II., page 86, which forms part of this discussion.
On page 87 the following passage occurs: "I shall have to discuss and
think more about your difficulty of the temperate and sub-arctic forms
in the S. hemisphere than I have yet done. But I am inclined to think
that I am right (if my general principles are right), that there would
be little tendency to the formation of a new species during the period
of migration, whether shorter or longer, though considerable variability
may have supervened.)

LETTER 337. TO J.D. HOOKER. Down, December 10th [1856].

It is a most tiresome drawback to my satisfaction in writing that,
though I leave out a good deal and try to condense, every chapter
runs to such an inordinate length. My present chapter on the causes of
fertility and sterility and on natural crossing has actually run out
to 100 pages MS., and yet I do not think I have put in anything
superfluous...

I have for the last fifteen months been tormented and haunted by
land-mollusca, which occur on every oceanic island; and I thought that
the double creationists or continental extensionists