your photograph, for one likes to have a picture in one's mind of
any one about whom one is interested. I have received and read with
interest your paper on the sponge with horny spicula. (188/1. "Ueber
Darwinella aurea, einen Schwamm mit sternformigen Hornnadeln."--"Archiv.
Mikrosk. Anat." I., page 57, 1866.) Owing to ill-health, and being
busy when formerly well, I have for some years neglected periodical
scientific literature, and have lately been reading up, and have thus
read translations of several of your papers; amongst which I have been
particularly glad to read and see the drawings of the metamorphoses
of Peneus. (188/2. "On the Metamorphoses of the Prawns," by Dr. Fritz
Muller.--"Ann. Mag. Nat. Hist." Volume XIV., page 104 (with plate),
1864. Translated by W.S. Dallas from "Wiegmann's Archiv," 1863 (see also
"Facts and Arguments for Darwin," passim, translated by W.S. Dallas:
London, 1869).) This seems to me the most interesting discovery in
embryology which has been made for years.

I am much obliged to you for telling me a little of your plans for the
future; what a strange, but to my taste interesting life you will lead
when you retire to your estate on the Itajahy!

You refer in your letter to the facts which Agassiz is collecting,
against our views, on the Amazons. Though he has done so much for
science, he seems to me so wild and paradoxical in all his views that I
cannot regard his opinions as of any value.

LETTER 189. TO A.R. WALLACE. Down, January 22nd, 1866.

I thank you for your paper on pigeons (189/1. "On the Pigeons of the
Malay Archipelago" (The "Ibis," October, 1865). Mr. Wallace points out
(page 366) that "the most striking superabundance of pigeons, as well
as of parrots, is confined to the Australo-Malayan sub-region in
which...the forest-haunting and fruit-eating mammals, such as monkeys
and squirrels, are totally absent." He points out also that monkeys are
"exceedingly destructive to eggs and young birds."), which interested
me, as everything that you write does. Who would ever have dreamed that
monkeys influenced the distribution of pigeons and parrots! But I have
had a still higher satisfaction, for I finished your paper yesterday in
the "Linnean Transactions." (189/2. "Linn. Soc. Trans." XXV.: a paper
on the geographical distribution and variability of the Malayan
Papilionidae.) It is admirably done. I cannot conceive that the most
firm believer in species could read it without