No fact of your letter has interested me more than that about mimicry.
It is a capital fact about the males pursuing the wrong females. You put the difficulty of the first steps in imitation in a most striking and CONVINCING manner. Your idea of s.e.xual selection having aided protective imitation interests me greatly, for the same idea had occurred to me in quite different cases, viz. the dulness of all animals in the Galapagos Islands, Patagonia, etc., and in some other cases; but I was afraid even to hint at such an idea. Would you object to my giving some such sentence as follows: "F. Muller suspects that s.e.xual selection may have come into play, in aid of protective imitation, in a very peculiar manner, which will appear extremely improbable to those who do not fully believe in s.e.xual selection. It is that the appreciation of certain colour is developed in those species which frequently behold other species thus ornamented." Again let me thank you cordially for your most interesting letter...
CHARLES DARWIN TO E.B. TYLOR. Down, [September 24, 1871].
My dear Sir,
I hope that you will allow me to have the pleasure of telling you how greatly I have been interested by your "Primitive Culture," now that I have finished it. It seems to me a most profound work, which will be certain to have permanent value, and to be referred to for years to come. It is wonderful how you trace animism from the lower races up to the religious belief of the highest races. It will make me for the future look at religion--a belief in the soul, etc.--from a new point of view. How curious, also, are the survivals or rudiments of old customs... You will perhaps be surprised at my writing at so late a period, but I have had the book read aloud to me, and from much ill-health of late could only stand occasional short reads. The undertaking must have cost you gigantic labour. Nevertheless, I earnestly hope that you may be induced to treat morals in the same enlarged yet careful manner, as you have animism. I fancy from the last chapter that you have thought of this. No man could do the work so well as you, and the subject a.s.suredly is a most important and interesting one. You must now possess references which would guide you to a sound estimation of the morals of savages; and how writers like Wallace, Lubbock, etc., etc., do differ on this head. Forgive me for troubling you, and believe me, with much respect,
Yours very sincerely, CH. DARWIN.
1872.
[At the beginning of the year the sixth edition of the "Origin," which had been begun in June, 1871, was nearly completed. The last sheet was revised on January 10, 1872, and the book was published in the course of the month. This volume differs from the previous ones in appearance and size--it consists of 458 pages instead of 596 pages and is a few ounces lighter; it is printed on bad paper, in small type, and with the lines unpleasantly close together. It had, however, one advantage over previous editions, namely that it was issued at a lower price. It is to be regretted that this the final edition of the "Origin" should have appeared in so unattractive a form; a form which has doubtless kept off many readers from the book.
The discussion suggested by the "Genesis of Species" was perhaps the most important addition to the book. The objection that incipient structures cannot be of use was dealt with in some detail, because it seemed to the author that this was the point in Mr. Mivart"s book which has struck most readers in England.
It is a striking proof of how wide and general had become the acceptance of his views that my father found it necessary to insert (sixth edition, page 424), the sentence: "As a record of a former state of things, I have retained in the foregoing paragraphs and also elsewhere, several sentences which imply that naturalists believe in the separate creation of each species; and I have been much censured for having thus expressed myself. But undoubtedly this was the general belief when the first edition of the present work appeared... Now things are wholly changed, and almost every naturalist admits the great principle of evolution."
A small correction introduced into this sixth edition is connected with one of his minor papers: "Note on the habits of the Pampas Woodp.e.c.k.e.r."
(Zoolog. Soc. Proc. 1870.) In the fifth edition of the "Origin," page 220, he wrote:--
"Yet as I can a.s.sert not only from my own observation, but from that of the accurate Azara, it [the ground woodp.e.c.k.e.r] never climbs a tree." The paper in question was a reply to Mr. Hudson"s remarks on the woodp.e.c.k.e.r in a previous number of the same journal. The last sentence of my father"s paper is worth quoting for its temperate tone: "Finally, I trust that Mr. Hudson is mistaken when he says that any one acquainted with the habits of this bird might be induced to believe that I "had purposely wrested the truth" in order to prove my theory. He exonerates me from this charge; but I should be loath to think that there are many naturalists who, without any evidence, would accuse a fellow-worker of telling a deliberate falsehood to prove his theory." In the sixth edition, page 142, the pa.s.sage runs "in certain large districts it does not climb trees." And he goes on to give Mr. Hudson"s statement that in other regions it does frequent trees.
One of the additions in the sixth edition (page 149), was a reference to Mr. A. Hyatt"s and Professor Cope"s theory of "acceleration." With regard to this he wrote (October 10, 1872) in characteristic words to Mr. Hyatt:--
"Permit me to take this opportunity to express my sincere regret at having committed two grave errors in the last edition of my "Origin of Species," in my allusion to yours and Professor Cope"s views on acceleration and r.e.t.a.r.dation of development. I had thought that Professor Cope had preceded you; but I now well remember having formerly read with lively interest, and marked, a paper by you somewhere in my library, on fossil Cephalapods with remarks on the subject. It seems also that I have quite misrepresented your joint view. This has vexed me much. I confess that I have never been able to grasp fully what you wish to show, and I presume that this must be owing to some dulness on my part."
Lastly, it may be mentioned that this cheap edition being to some extent intended as a popular one, was made to include a glossary of technical terms, "given because several readers have complained... that some of the terms used were unintelligible to them." The glossary was compiled by Mr. Dallas, and being an excellent collection of clear and sufficient definitions, must have proved useful to many readers.]
CHARLES DARWIN TO J.L.A. DE QUATREf.a.gES. Down, January 15, 1872.
My dear Sir,
I am much obliged for your very kind letter and exertions in my favour.
I had thought that the publication of my last book ["Descent of Man"]
would have destroyed all your sympathy with me, but though I estimated very highly your great liberality of mind, it seems that I underrated it.
I am gratified to hear that M. Lacaze-Duthiers will vote (He was not elected as a corresponding member of the French Academy until 1878.) for me, for I have long honoured his name. I cannot help regretting that you should expend your valuable time in trying to obtain for me the honour of election, for I fear, judging from the last time, that all your labour will be in vain. Whatever the result may be, I shall always retain the most lively recollection of your sympathy and kindness, and this will quite console me for my rejection.
With much respect and esteem, I remain, dear Sir,
Yours truly obliged, CHARLES DARWIN.
P.S.--With respect to the great stress which you lay on man walking on two legs, whilst the quadrumana go on all fours, permit me to remind you that no one much values the great difference in the mode of locomotion, and consequently in structure, between seals and the terrestrial carnivora, or between the almost biped kangaroos and other marsupials.
CHARLES DARWIN TO AUGUST WEISMANN. (Professor of Zoology in Freiburg.) Down, April 5, 1872.
My dear Sir,
I have now read your essay ("Ueber den Einfluss der Isolirung auf die Artbildung." Leipzig, 1872.) with very great interest. Your view of the "Origin" of local races through "Amixie," is altogether new to me, and seems to throw an important light on an obscure problem. There is, however, something strange about the periods or endurance of variability. I formerly endeavoured to investigate the subject, not by looking to past time, but to species of the same genus widely distributed; and I found in many cases that all the species, with perhaps one or two exceptions, were variable. It would be a very interesting subject for a conchologist to investigate, viz., whether the species of the same genus were variable during many successive geological formations. I began to make enquiries on this head, but failed in this, as in so many other things, from the want of time and strength. In your remarks on crossing, you do not, as it seems to me, lay nearly stress enough on the increased vigour of the offspring derived from parents which have been exposed to different conditions. I have during the last five years been making experiments on this subject with plants, and have been astonished at the results, which have not yet been published.
In the first part of your essay, I thought that you wasted (to use an English expression) too much powder and shot on M. Wagner (Prof. Wagner has written two essays on the same subject. "Die Darwin"sche Theorie und das Migrationsgesetz, in 1868, and "Ueber den Einfluss der Geographischen Isolirung, etc.," an address to the Bavarian Academy of Sciences at Munich, 1870.); but I changed my opinion when I saw how admirably you treated the whole case, and how well you used the facts about the Planorbis. I wish I had studied this latter case more carefully. The manner in which, as you show, the different varieties blend together and make a constant whole, agrees perfectly with my hypothetical ill.u.s.trations.
Many years ago the late E. Forbes described three closely consecutive beds in a secondary formation, each with representative forms of the same fres-water sh.e.l.ls: the case is evidently a.n.a.logous with that of Hilgendorf ("Ueber Planorbis multiformis im Steinheimer Susswa.s.ser-kalk." Monatsbericht of the Berlin Academy, 1866.), but the interesting connecting varieties or links were here absent. I rejoice to think that I formerly said as emphatically as I could, that neither isolation nor time by themselves do anything for the modification of species. Hardly anything in your essay has pleased me so much personally, as to find that you believe to a certain extent in s.e.xual selection. As far as I can judge, very few naturalists believe in this.
I may have erred on many points, and extended the doctrine too far, but I feel a strong conviction that s.e.xual selection will hereafter be admitted to be a powerful agency. I cannot agree with what you say about the taste for beauty in animals not easily varying. It may be suspected that even the habit of viewing differently coloured surrounding objects would influence their taste, and Fritz Muller even goes so far as to believe that the sight of gaudy b.u.t.terflies might influence the taste of distinct species. There are many remarks and statements in your essay which have interested me greatly, and I thank you for the pleasure which I have received from reading it.
With sincere respect, I remain, My dear Sir, yours very faithfully, CHARLES DARWIN.
P.S.--If you should ever be induced to consider the whole doctrine of s.e.xual selection, I think that you will be led to the conclusion, that characters thus gained by one s.e.x are very commonly transferred in a greater or less degree to the other s.e.x.
[With regard to Moritz Wagner"s first Essay, my father wrote to that naturalist, apparently in 1868:]
Dear and respected Sir,
I thank you sincerely for sending me your "Migrationsgesetz, etc.," and for the very kind and most honourable notice which you have taken of my works. That a naturalist who has travelled into so many and such distant regions, and who has studied animals of so many cla.s.ses, should, to a considerable extent, agree with me, is, I can a.s.sure you, the highest gratification of which I am capable... Although I saw the effects of isolation in the case of islands and mountain-ranges, and knew of a few instances of rivers, yet the greater number of your facts were quite unknown to me. I now see that from the want of knowledge I did not make nearly sufficient use of the views which you advocate; and I almost wish I could believe in its importance to the same extent with you; for you well show, in a manner which never occurred to me, that it removes many difficulties and objections. But I must still believe that in many large areas all the individuals of the same species have been slowly modified, in the same manner, for instance, as the English race-horse has been improved, that is by the continued selection of the fleetest individuals, without any separation. But I admit that by this process two or more new species could hardly be found within the same limited area; some degree of separation, if not indispensable, would be highly advantageous; and here your facts and views will be of great value...
[The following letter bears on the same subject. It refers to Professor M. Wagner"s Essay, published in "Das Ausland", May 31, 1875:]
CHARLES DARWIN TO MORITZ WAGNER. Down, October 13, 1876.
Dear Sir,
I have now finished reading your essays, which have interested me in a very high degree, notwithstanding that I differ much from you on various points. For instance, several considerations make me doubt whether species are much more variable at one period than at another, except through the agency of changed conditions. I wish, however, that I could believe in this doctrine, as it removes many difficulties. But my strongest objection to your theory is that it does not explain the manifold adaptations in structure in every organic being--for instance in a Picus for climbing trees and catching insects--or in a Strix for catching animals at night, and so on ad infinitum. No theory is in the least satisfactory to me unless it clearly explains such adaptations. I think that you misunderstand my views on isolation. I believe that all the individuals of a species can be slowly modified within the same district, in nearly the same manner as man effects by what I have called the process of unconscious selection... I do not believe that one species will give birth to two or more new species as long as they are mingled together within the same district. Nevertheless I cannot doubt that many new species have been simultaneously developed within the same large continental area; and in my "Origin of Species" I endeavoured to explain how two new species might be developed, although they met and intermingled on the BORDERS of their range. It would have been a strange fact if I had overlooked the importance of isolation, seeing that it was such cases as that of the Galapagos Archipelago, which chiefly led me to study the origin of species. In my opinion the greatest error which I have committed, has been not allowing sufficient weight to the direct action of the environment, i.e. food, climate, etc., independently of natural selection. Modifications thus caused, which are neither of advantage nor disadvantage to the modified organism, would be especially favoured, as I can now see chiefly through your observations, by isolation in a small area, where only a few individuals lived under nearly uniform conditions.
When I wrote the "Origin," and for some years afterwards, I could find little good evidence of the direct action of the environment; now there is a large body of evidence, and your case of the Saturnia is one of the most remarkable of which I have heard. Although we differ so greatly, I hope that you will permit me to express my respect for your long-continued and successful labours in the good cause of natural science.
I remain, dear Sir, yours very faithfully, CHARLES DARWIN.
[The two following letters are also of interest as bearing on my father"s views on the action of isolation as regards the origin of new species:]
CHARLES DARWIN TO K. SEMPER. Down, November 26, 1878.
My dear Professor Semper,
When I published the sixth edition of the "Origin," I thought a good deal on the subject to which you refer, and the opinion therein expressed was my deliberate conviction. I went as far as I could, perhaps too far in agreement with Wagner; since that time I have seen no reason to change my mind, but then I must add that my attention has been absorbed on other subjects. There are two different cla.s.ses of cases, as it appears to me, viz. those in which a species becomes slowly modified in the same country (of which I cannot doubt there are innumerable instances) and those cases in which a species splits into two or three or more new species, and in the latter case, I should think nearly perfect separation would greatly aid in their "specification," to coin a new word.
I am very glad that you are taking up this subject, for you will be sure to throw much light on it. I remember well, long ago, oscillating much; when I thought of the Fauna and Flora of the Galapagos Islands I was all for isolation, when I thought of S. America I doubted much. Pray believe me,
Yours very sincerely,