ife and Letters," II., page 112.) Hartung
could hardly be mistaken about granite blocks on a volcanic island.

I do not think it a mystery that birds have not been modified in
Madeira. (370/2. "Origin," Edition VI., page 328. Madeira has only one
endemic bird. Darwin accounts for the fact from the island having been
stocked with birds which had struggled together and become mutually
co-adapted on the neighbouring continents. "Hence, when settled in their
new homes, each kind will have been kept by the others in its proper
place and habits, and will consequently have been but little liable to
modification." Crossing with frequently arriving immigrants will also
tend to keep down modification.) Pray look at page 422 of "Origin"
[Edition III.]. You would not think it a mystery if you had seen the
long lists which I have (somewhere) of the birds annually blown, even in
flocks, to Madeira. The crossed stock would be the more vigorous.

Remember if you do not come here before Nottingham, if you do not come
afterwards I shall think myself diabolically ill-used.

LETTER 371. J.D. HOOKER TO CHARLES DARWIN. Kew, August 9th, 1866.

If my letters did not gene you it is impossible that you should suppose
that yours were of no use to me! I would throw up the whole thing were
it not for correspondence with you, which is the only bit of silver
in the affair. I do feel it disgusting to have to make a point of a
speciality in which I cannot see my way a bit further than I could
before I began. To be sure, I have a very much clearer notion of the
pros and cons on both sides (though these were rather forgotten facts
than rediscoveries). I see the sides of the well further down more
distinctly, but the bottom is as obscure as ever.

I think I know the "Origin" by heart in relation to the subject, and
it was reading it that suggested the queries about Azores boulders and
Madeira birds. The former you and I have talked over, and I thought I
remembered that you wanted it confirmed. The latter strikes me thus: why
should plants and insects have been so extensively changed and birds not
at all? I perfectly understand and feel the force of your argument in
reference to birds per se, but why do these not apply to insects and
plants? Can you not see that this suggests the conclusion that the
plants are derived one way and the birds another?

I certainly did take it for granted that you supposed the stocking [by]
occasional transport to be so