I cannot give you facts, and I must write dogmatically, though I do not feel so on any point. I may just mention, in order that you may believe that I have SOME foundation for my views, that Hooker has read my MS., and though he at first demurred to my main point, he has since told me that further reflection and new facts have made him a convert.
In the older, or perhaps newer, Pliocene age (a little BEFORE the Glacial epoch) the temperature was higher; of this there can be little doubt; the land, on a LARGE SCALE, held much its present disposition: the species were mainly, judging from sh.e.l.ls, what they are now. At this period when all animals and plants ranged 10 or 15 degrees nearer the poles, I believe the northern part of Siberia and of North America being almost CONTINUOUS, were peopled (it is quite possible, considering the shallow water, that Behring Straits were united, perhaps a little southward) by a nearly uniform fauna and flora, just as the Arctic regions now are. The climate then became gradually colder till it became what it now is; and then the temperate parts of Europe and America would be separated, as far as migration is concerned, just as they now are.
Then came on the Glacial period, driving far south all living things; middle or even southern Europe being peopled with Arctic productions; as the warmth returned, the Arctic productions slowly crawled up the mountains as they became denuded of snow; and we now see on their summits the remnants of a once continuous flora and fauna. This is E.
Forbes" theory, which, however, I may add, I had written out four years before he published.
Some facts have made me vaguely SUSPECT that between the glacial and the present temperature there was a period of SLIGHTLY greater warmth.
According to my modification-doctrines, I look at many of the species of North America which CLOSELY represent those of Europe, as having become modified since the Pliocene period, when in the northern part of the world there was nearly free communication between the old and new worlds. But now comes a more important consideration; there is a considerable body of geological evidence that during the Glacial epoch the whole world was colder; I inferred that, many years ago, from erratic boulder phenomena carefully observed by me on both the east and west coast of South America. Now I am so bold as to believe that at the height of the Glacial epoch, AND WHEN ALL TROPICAL PRODUCTIONS MUST HAVE BEEN CONSIDERABLY DISTRESSED, that several temperate forms slowly travelled into the heart of the Tropics, and even reached the southern hemisphere; and some few southern forms penetrated in a reverse direction northward. (Heights of Borneo with Australian forms, Abyssinia with Cape forms.) Wherever there was nearly continuous HIGH land, this migration would have been immensely facilitated; hence the European character of the plants of Tierra del Fuego and summits of Cordilleras; hence ditto on Himalaya. As the temperature rose, all the temperate intruders would crawl up the mountains. Hence the European forms on Nilgherries, Ceylon, summit of Java, Organ Mountains of Brazil. But these intruders being surrounded with new forms would be very liable to be improved or modified by natural selection, to adapt them to the new forms with which they had to compete; hence most of the forms on the mountains of the Tropics are not identical, but REPRESENTATIVE forms of North temperate plants.
There are similar cla.s.ses of facts in marine productions. All this will appear very rash to you, and rash it may be; but I am sure not so rash as it will at first appear to you: Hooker could not stomach it at all at first, but has become largely a convert. From mammalia and shallow sea, I believe j.a.pan to have been joined to main land of China within no remote period; and then the migration north and south before, during, and after the Glacial epoch would act on j.a.pan, as on the corresponding lat.i.tude of China and the United States.
I should beyond anything like to know whether you have any Alpine collections from j.a.pan, and what is their character. This letter is miserably expressed, but perhaps it will suffice to show what I believe have been the later main migrations and changes of temperature...
CHARLES DARWIN TO J.D. HOOKER. [Down] October 6th, 1858.
...If you have or can make leisure, I should very much like to hear news of Mrs. Hooker, yourself, and the children. Where did you go, and what did you do and are doing? There is a comprehensive text.
You cannot tell how I enjoyed your little visit here, it did me much good. If Harvey is still with you, pray remember me very kindly to him.
...I am working most steadily at my Abstract, but it grows to an inordinate length; yet fully to make my view clear (and never giving briefly more than a fact or two, and slurring over difficulties), I cannot make it shorter. It will yet take me three or four months; so slow do I work, though never idle. You cannot imagine what a service you have done me in making me make this Abstract; for though I thought I had got all clear, it has clarified my brains very much, by making me weigh the relative importance of the several elements.
I have been reading with much interest your (as I believe it to be) capital memoir of R. Brown in the "Gardeners" Chronicle"...
CHARLES DARWIN TO J.D. HOOKER. Down, October 12th, [1858].
...I have sent eight copies (Of the joint paper by C. Darwin and A.R.
Wallace.) by post to Wallace, and will keep the others for him, for I could not think of any one to send any to.
I pray you not to p.r.o.nounce too strongly against Natural Selection, till you have read my abstract, for though I dare say you will strike out MANY difficulties, which have never occurred to me; yet you cannot have thought so fully on the subject as I have.
I expect my Abstract will run into a small volume, which will have to be published separately...
What a splendid lot of work you have in hand.
Ever yours, C. DARWIN.
CHARLES DARWIN TO J.D. HOOKER. Down, October 13th [1858].
...I have been a little vexed at myself at having asked you not "to p.r.o.nounce too strongly against Natural Selection." I am sorry to have bothered you, though I have been much interested by your note in answer.
I wrote the sentence without reflection. But the truth is, that I have so accustomed myself, partly from being quizzed by my non-naturalist relations, to expect opposition and even contempt, that I forgot for the moment that you are the one living soul from whom I have constantly received sympathy. Believe [me] that I never forget for even a minute how much a.s.sistance I have received from you. You are quite correct that I never even suspected that my speculations were a "jam-pot" to you; indeed, I thought, until quite lately, that my MS. had produced no effect on you, and this has often staggered me. Nor did I know that you had spoken in general terms about my work to our friends, excepting to dear old Falconer, who some few years ago once told me that I should do more mischief than any ten other naturalists would do good, [and] that I had half spoiled you already! All this is stupid egotistical stuff, and I write it only because you may think me ungrateful for not having valued and understood your sympathy; which G.o.d knows is not the case. It is an accursed evil to a man to become so absorbed in any subject as I am in mine.
I was in London yesterday for a few hours with Falconer, and he gave me a magnificent lecture on the age of man. We are not upstarts; we can boast of a pedigree going far back in time coeval with extinct species.
He has a grand fact of some large molar tooth in the Trias.
I am quite knocked up, and am going next Monday to revive under Water-cure at Moor Park.
My dear Hooker, yours affectionately, C. DARWIN.
CHARLES DARWIN TO J.D. HOOKER. November 1858.
...I had vowed not to mention my everlasting Abstract to you again, for I am sure I have bothered you far more than enough about it; but, as you allude to its previous publication, I may say that I have the chapters on Instinct and Hybridism to abstract, which may take a fortnight each; and my materials for Palaeontology, Geographical Distribution, and Affinities, being less worked up, I dare say each of these will take me three weeks, so that I shall not have done at soonest till April, and then my Abstract will in bulk make a small volume. I never give more than one or two instances, and I pa.s.s over briefly all difficulties, and yet I cannot make my Abstract shorter, to be satisfactory, than I am now doing, and yet it will expand to a small volume...
[About this time my father revived his old knowledge of beetles in helping his boys in their collecting. He sent a short notice to the "Entomologist"s Weekly Intelligencer," June 25th, 1859, recording the capture of Licinus silphoides, Clytus mysticus, Panagaeus 4-pustulatus.
The notice begins with the words, "We three very young collectors having lately taken in the parish of Down," etc., and is signed by three of his boys, but was clearly not written by them. I have a vivid recollection of the pleasure of turning out my bottle of dead beetles for my father to name, and the excitement, in which he fully shared, when any of them proved to be uncommon ones. The following letters to Mr. Fox (November 13, 1858), and to Sir John Lubbock, ill.u.s.trate this point:]
CHARLES DARWIN TO W.D. FOX. Down, November 13th [1858].
...W., my son, is now at Christ"s College, in the rooms above yours.
My old Gyp, Impey, was astounded to hear that he was my son, and very simply asked, "Why, has he been long married?" What pleasant hours those were when I used to come and drink coffee with you daily! I am reminded of old days by my third boy having just begun collecting beetles, and he caught the other day Brachinus crepitans, of immortal Whittlesea Mere memory. My blood boiled with old ardour when he caught a Licinus--a prize unknown to me...
CHARLES DARWIN TO JOHN LUBBOCK. Thursday [before 1857].
Dear Lubbock,
I do not know whether you care about beetles, but for the chance I send this in a bottle, which I never remember having seen; though it is excessively rash to speak from a twenty-five-year old remembrance.
Whenever we meet you can tell me whether you know it...
I feel like an old war-horse at the sound of the trumpet, when I read about the capturing of rare beetles--is not this a magnanimous simile for a decayed entomologist?--It really almost makes me long to begin collecting again. Adios.
"Floreat Entomologia"!--to which toast at Cambridge I have drunk many a gla.s.s of wine. So again, "Floreat Entomologia." N.B. I have NOT now been drinking any gla.s.ses full of wine.
Yours, C.D.
CHARLES DARWIN TO HERBERT SPENCER. Down, November 25th [1858].
Dear Sir,
I beg permission to thank you sincerely for your very kind present of your Essays. ("Essays, Scientific, Political, and Speculative," by Herbert Spencer, 1858-74.) I have already read several of them with much interest. Your remarks on the general argument of the so-called development theory seems to me admirable. I am at present preparing an Abstract of a larger work on the changes of species; but I treat the subject simply as a naturalist, and not from a general point of view, otherwise, in my opinion, your argument could not have been improved on, and might have been quoted by me with great advantage. Your article on Music has also interested me much, for I had often thought on the subject, and had come to nearly the same conclusion with you, though unable to support the notion in any detail. Furthermore, by a curious coincidence, expression has been for years a persistent subject with me for LOOSE speculation, and I must entirely agree with you that all expression has some biological meaning. I hope to profit by your criticism on style, and with very best thanks, I beg leave to remain, dear Sir,
Yours truly obliged, C. DARWIN.
CHARLES DARWIN TO J.D. HOOKER. Down, December 24th [1858].
My dear Hooker,
Your news about your unsolicited salary and house is jolly, and creditable to the Government. My room (28 x 19), with divided room above, with ALL FIXTURES (and painted), not furniture, and plastered outside, cost about 500 pounds. I am heartily glad of this news.
Your facts about distribution are, indeed, very striking. I remember well that none of your many wonderful facts in your several works, perplexed me, for years, more than the migration having been mainly from north to south, and not in the reverse direction. 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 compet.i.tion 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.