My dear Hooker

Manny thanks for Acropera & about the book. I will take your letter seriatim.² There is good evidence that S.E. England was dry land during glacial period. I forget what Austin says but mammals prove, I think, that England has been united to the Continent since the glacial period.³ I don’t see your difficulty about what I say on the breaking of an isthmus: if Panama was broken thro’, w^d. not the fauna of the Pacific flow into the W. Indies, or vice versâ, & destroy a multitude of creatures.⁴ Of course I’m no judge, but I thought De Candolle had made out his case about small areas of trees—⁵ You will find at P. 112 3^rd. edit. Origin a too concise allusion to the Madeira flora being a remnant of the tertiary European flora.⁶

I shall feel deeply interested by reading your botanical difficuties against occasional immigration. The facts you give about certain plants such as the Heaths are certainly very curious. I thought the Azores flora was more boreal: but what can you mean by saying that the Azores are nearer to Britain & Newfoundland than to Madeira? on the Globe they are nearly twice as far off.⁷ With respect to sea-currents, I formerly made enquiries at Madeira but cannot now give you the results but I remember that the facts were different from what is generally stated; I think that a ship wrecked on the Canary Islands was thrown up on the coast of Madeira.⁸ You speak as if only land shells differed in Madeira & P^o. Santo: does my memory deceive me that there is a host of representative insects?⁹

When you exorcise at Nottingham occasional means of transport, be honest, & admit how little is known on the subject.¹⁰ Remember how recently you & others thought that Salt-water would soon kill seeds.¹¹ Reflect that there is not a coral-islet in the ocean which is not pretty well clothed with plants: & the fewness of the species can hardly with justice be attributed to the arrival of few seeds, for coral-Islets close to other land support only the same limited vegetation.¹² Remember that no one knew that seeds w^d remain for many hours in the crops of birds & retain their vitality; that fish eat seeds & that when the fish are devoured by birds the seeds can germinate &c &c—¹³ Remember that every year many birds are blown to Madeira & to the Bermudas. Remember that dust is blown 1000 miles over the Atlantic.¹⁴ Now bearing all this in mind, w^d it not be a prodigy if an unstocked Island did not in the course of ages receive colonists from coasts, whence the currents flow, trees are drifted, & birds are driven by gales. The objections to islands being thus stocked are, as far as I understand, that certain species & genera have been more freely introduced & others less freely than might have been expected. But then the sea kills some sorts of seeds, others are killed by the digestion of birds & some w^d be more liable than others to adhere to birds feet; but we know so very little on these points that it seems to me that we cannot at all tell what forms w^d probably be introduced & what w^d not.¹⁵

I do not for a moment pretend that these means of introduction can be proved to have acted; but they seem to me sufficient, with no valid or heavy objections, whilst there are, as it seems to me, the heaviest objections, on geological & on geographical-Distribution grounds, (p. 387, 388, Origin) to Forbes’ enormous continental extensions.¹⁶ But I fear that I shall & have bored you.—

Yours ever affect— | C. Darwin.

P.S. Murray will not bring out, & be hanged to him, the new Edit. of Origin, though all printed off, till November.—¹⁷ I have persuaded him to send Lyell a copy; I do not suppose you w^d. care to have your copy at once; if you did, I would ask Murray, but for some reason, he does not seem much to like sending out the copies.—¹⁸

Dont answer unless you like, for you must be very busy.—

P.S. Here is a bad job, the Acropera has not arrived.— I hope it was not sent off, as soon as you thought. I sent this evening (Friday) but no parcel at Station. If not there tomorrow it must be lost. It is a bad job for me & for you, if the plant is valuable.—¹⁹

P.S. 2^d. As you were asking about Books on “Origin”; a very good Zoologist Claus has just published one, with my name on title-page—the subject being an investigation of the amount of individual variability in the Copepodous Crustaceans & he shows it is wonderfully great in many organs & that some co existing vars, are apparently passing into distinct species.—²⁰

☞Acropera all safe Saturday morning