Helena, instead of which I believe they are very poor [in] peculiar
genera. Have they all got submerged for a short time during the ups and
downs to which they have been subjected, Tahiti and some others having
been built up by volcanic action in the Pliocene period? Madeira and the
Canaries were islands in the Upper Miocene ocean, and may therefore well
have peculiar endemic types of very old date, and destroyed elsewhere. I
have just got in Wollaston's "Coleoptera Atlantidum," and shall be glad
to lend it you when I have read the Introduction. He goes in for
continental extension, which only costs him two catastrophes by which
the union and disunion with the nearest mainland may readily be
accomplished.... --Believe me ever most truly yours,
CHA. LYELL.
* * * * *
SIR C. LYELL TO A.R. WALLACE
_73 Harley Street. May 2, 1867._
My dear Sir,--I forgot to ask you last night about an ornithological
point which I have been discussing with the Duke of Argyll. In Chapter
V. of his "Reign of Law" (which I should be happy to lend you, if you
have time to look at it immediately) he treats of humming-birds, saying
that Gould has made out about 400 species, every one of them very
distinct from the other, and only one instance, in Ecuador, of a species
which varies in its tail-feathers in such a way as to make it doubtful
whether it ought to rank as a species, an opinion to which Gould
inclines, or only as a variety or incipient species, as the Duke thinks.
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