More Letters of Charles Darwin, vol 2 | Page 8

was "first separated [it] would have been
both much larger and much nearer the main island.") which I owe to
you. Was there ever such an enigma? If, in the course of a week or two,
you can find time to let me hear what you think, I should very much
like to hear: or we hope to be at Erasmus' on March 4th for a week.
Would there be any chance of your coming to luncheon then? What a
case it is. Palms, screw-pines, four snakes--not one being in main
island--lizards, insects, and not one land bird. But, above everything,
such a proportion of individual monocotyledons! The conditions do not
seem very different from the Tuff Galapagos Island, but, as far as I
remember, very few monocotyledons there. Then, again, the island
seems to have been elevated. I wonder much whether it stands out in
the line of any oceanic current, which does not so forcibly strike the
main island? But why, oh, why should so many monocotyledons have
come there? or why should they have survived there more than on the
main island, if once connected? So, again, I cannot conceive that four
snakes should have become extinct in Mauritius and survived on Round
Island. For a moment I thought that Mauritius might be the newer
island, but the enormous degradation which the outer ring of rocks has
undergone flatly contradicts this, and the marine remains on the summit
of Round Island indicate the island to be comparatively new--unless,
indeed, they are fossil and extinct marine remains. Do tell me what you
think. There never was such an enigma. I rather lean to separate
immigration, with, of course, subsequent modification; some forms, of
course, also coming from Mauritius. Speaking of Mauritius reminds me
that I was so much pleased the day before yesterday by reading a
review of a book on the geology of St. Helena, by an officer who knew

nothing of my hurried observations, but confirms nearly all that I have
said on the general structure of the island, and on its marvellous
denudation. The geology of that island was like a novel.

LETTER 387. TO A. BLYTT. Down, March 28th, 1876.
(387/1. The following refers to Blytt's "Essay on the Immigration of the
Norwegian Flora during Alternating Rainy and Dry Periods,"
Christiania, 1876.)
I thank you sincerely for your kindness in having sent me your work on
the "Immigration of the Norwegian Flora," which has interested me in
the highest degree. Your view, supported as it is by various facts,
appears to me the most important contribution towards understanding
the present distribution of plants, which has appeared since Forbes'
essay on the effects of the Glacial Period.
LETTER 388. TO AUG. FOREL. Down, June 19th, 1876.
I hope you will allow me to suggest an observation, should any
opportunity occur, on a point which has interested me for many
years--viz., how do the coleoptera which inhabit the nests of ants
colonise a new nest? Mr. Wallace, in reference to the presence of such
coleoptera in Madeira, suggests that their ova may be attached to the
winged female ants, and that these are occasionally blown across the
ocean to the island. It would be very interesting to discover whether the
ova are adhesive, and whether the female coleoptera are guided by
instinct to attach them to the female ants (388/1. Dr. Sharp is good
enough to tell us that he is not aware of any such adaptation. Broadly
speaking, the distribution of the nest-inhabiting beetles is due to
co-migration with the ants, though in some cases the ants transport the
beetles. Sitaris and Meloe are beetles which live "at the expense of bees
of the genus Anthophora." The eggs are laid not in but near the bees'
nest; in the early stage the larva is active and has the instinct to seize
any hairy object near it, and in this way they are carried by the
Anthophora to the nest. Dr. Sharp states that no such preliminary stage
is known in the ant's-nest beetles. For an account of Sitaris and Meloe,
see Sharp's "Insects," II., page 272.); or whether the larvae pass through
an early stage, as with Sitaris or Meloe, or cling to the bodies of the
females. This note obviously requires no answer. I trust that you
continue your most interesting investigations on ants.

(PLATE: MR. A.R. WALLACE, 1878. From a photograph by Maull &
Fox.)
LETTER 389. TO A.R. WALLACE.
(389/1. Published in "Life and Letters," III., page 230.)
(389/2. The following five letters refer to Mr. Wallace's "Geographical
Distribution of Animals," 1876.)
[Hopedene] (389/3. Mr. Hensleigh Wedgwood's house in Surrey.), June
5th, 1876.
I must have the pleasure of expressing to you my unbounded
admiration of your book (389/4. "Geographical Distribution," 1876.),
though