I have now at last satisfied MYSELF (but that is very different from satisfying others) on this head; but it would take a little volume to fully explain myself. I did not for long see the bearing of a conclusion, at which I had arrived, with respect to this subject. It is, that species inhabiting a very large area, and therefore existing in large numbers, and which have been subjected to the severest competition with many other forms, will have arrived, through natural selection, at a higher stage of perfection than the inhabitants of a small area. Thus I explain the fact of so many anomalies, or what may be called "living fossils," inhabiting now only fresh water, having been beaten out, and exterminated in the sea, by more improved forms; thus all existing Ganoid fishes are fresh water, as [are] Lepidosiren and Ornithorhynchus, etc. The plants of Europe and Asia, as being the largest territory, I look at as the most "improved," and therefore as being able to withstand the less-perfected Australian plants; [whilst] these could not resist the Indian. See how all the productions of New Zealand yield to those of Europe. I dare say you will think all this utter bosh, but I believe it to be solid truth.
You will, I think, admit that Australian plants, flourishing so in India, is no argument that they could hold their own against the ten thousand natural contingencies of other plants, insects, animals, etc., etc. With respect to South West Australia and the Cape, I am shut up, and can only d--n the whole case.
...You say you should like to see my MS., but you did read and approve of my long Glacial chapter, and I have not yet written my Abstract on the whole of the Geographical Distribution, nor shall I begin it for two or three weeks. But either Abstract or the old MS. I should be DELIGHTED to send you, especially the Abstract chapter...
I have now written 330 folio pages of my abstract, and it will require 150- 200 [more]; so that it will make a printed volume of 400 pages, and must be printed separately, which I think will be better in many respects. The subject really seems to me too large for discussion at any Society, and I believe religion would be brought in by men whom I know.
I am thinking of a 12mo volume, like Lyell's fourth or fifth edition of the 'Principles.'...
I have written you a scandalously long note. So now good-bye, my dear Hooker,
Ever yours, C. DARWIN.
CHARLES DARWIN TO J.D. HOOKER. Down, January 20th, 1859.
My dear Hooker,
I should very much like to borrow Heer at some future time, for I want to read nothing perplexing at present till my Abstract is done. Your last very instructive letter shall make me very cautious on the hyper- speculative points we have been discussing.
When you say you cannot master the train of thoughts, I know well enough that they are too doubtful and obscure to be mastered. I have often experienced what you call the humiliating feeling of getting more and more involved in doubt the more one thinks of the facts and reasoning on doubtful points. But I always comfort myself with thinking of the future, and in the full belief that the problems which we are just entering on, will some day be solved; and if we just break the ground we shall have done some service, even if we reap no harvest.
I quite agree that we only differ in DEGREE about the means of dispersal, and that I think a satisfactory amount of accordance. You put in a very striking manner the mutation of our continents, and I quite agree; I doubt only about our oceans.
I also agree (I am in a very agreeing frame of mind) with your argumentum ad hominem, about the highness of the Australian Flora from the number of species and genera; but here comes in a superlative bothering element of doubt, viz., the effect of isolation.
The only point in which I PRESUMPTUOUSLY rather demur is about the status of the naturalised plants in Australia. I think Muller speaks of their having spread largely beyond cultivated ground; and I can hardly believe that our European plants would occupy stations so barren that the native plants could not live there.