ronger and stronger. I am very glad to hear about S.E. and
S.W. Australia: I suspected after my letter was gone that the case must
be as it is. You know of course that nearly the same rule holds with
birds and mammals. Several years ago I reviewed in the "Annals of
Natural History," (341/2. "Annals and Mag. of Nat. Hist." Volume XIX.,
1847, pages 53-56, an unsigned review of "A Natural History of the
Mammalia," by G.R. Waterhouse, Volume I. The passage referred to is
at page 55: "The fact of South Australia possessing only few peculiar
species, it having been apparently colonised from the eastern and
western coasts, is very interesting; for we believe that Mr. Robert
Brown has shown that nearly the same remark is applicable to the plants;
and Mr. Gould finds that most of the birds from these opposite shores,
though closely allied, are distinct. Considering these facts, together
with the presence in South Australia of upraised modern Tertiary
deposits and of extinct volcanoes, it seems probable that the eastern
and western shores once formed two islands, separated from each other
by a shallow sea, with their inhabitants generically, though not
specifically, related, exactly as are those of New Guinea and Northern
Australia, and that within a geologically recent period a series of
upheavals converted the intermediate sea into those desert plains which
are now known to stretch from the southern coast far northward, and
which then became colonised from the regions to the east and west." On
this point see Hooker's "Introductory Essay to the Flora of Tasmania,"
page ci, where Jukes' views are discussed. For an interesting account
of the bearings of the submergence of parts of Australia, see
Thiselton-Dyer, "R. Geogr. Soc. Jour." XXII., No. 6.) Waterhouse's
"Mammalia," and speculated that these two corners, now separated by gulf
and low land, must have existed as two large islands; but it is odd that
productions have not become more mingled; but it accords with, I think,
a very general rule in the spreading of organic beings. I agree with
what you say about Lyell; he learns more by word of mouth than by
reading.

Henslow has just gone, and has left me in a fit of enthusiastic
admiration of his character. He is a really noble and good man.

LETTER 342. TO G. BENTHAM. Down, December 1st [1858?].

I thank you for so kindly taking the trouble of writing to me, on
naturalised plants. I did not know of, or had forgotten, the clo