Volume I Part 41 (1/2)
I suppose my memory is wrong, but it tells me that these flowers are female, and I think that I once got a seed from one of them; but my memory may be quite wrong. I hope that you will continue your interesting researches.
LETTER 266. TO G. JAGER. Down, February 3rd, 1875.
I received this morning a copy of your work ”Contra Wigand,” either from yourself or from your publisher, and I am greatly obliged for it. (266/1. Jager's ”In Sachen Darwins insbesondere contra Wigand”
(Stuttgart, 1874) is directed against A. Wigand's ”Der Darwinismus und die Naturforschung Newtons und Cuviers” (Brunswick, 1874).) I had, however, before bought a copy, and have sent the new one to our best library, that of the Royal Society. As I am a very poor german scholar, I have as yet read only about forty pages; but these have interested me in the highest degree. Your remarks on fixed and variable species deserve the greatest attention; but I am not at present quite convinced that there are such independent of the conditions to which they are subjected. I think you have done great service to the principle of evolution, which we both support, by publis.h.i.+ng this work. I am the more glad to read it as I had not time to read Wigand's great and tedious volume.
LETTER 267. TO CHAUNCEY WRIGHT. Down, March 13th, 1875.
I write to-day so that there shall be no delay this time in thanking you for your interesting and long letter received this morning. I am sure that you will excuse brevity when I tell you that I am half-killing myself in trying to get a book ready for the press. (267/1. The MS. of ”Insectivorous Plants” was got ready for press in March, 1875. Darwin seems to have been more than usually oppressed by the work.) I quite agree with what you say about advantages of various degrees of importance being co-selected (267/2. Mr. Chauncey Wright wrote (February 24th, 1875): ”The inquiry as to which of several real uses is the one through which Natural Selection has acted...has for several years seemed to me a somewhat less important question than it seemed formerly, and still appears to most thinkers on the subject...The uses of the rattling of the rattlesnake as a protection by warning its enemies and as a s.e.xual call are not rival uses; neither are the high-reaching and the far-seeing uses of the giraffe's neck 'rivals.'”), and aided by the effects of use, etc. The subject seems to me well worth further development. I do not think I have anywhere noticed the use of the eyebrows, but have long known that they protected the eyes from sweat.
During the voyage of the ”Beagle” one of the men ascended a lofty hill during a very hot day. He had small eyebrows, and his eyes became fearfully inflamed from the sweat running into them. The Portuguese inhabitants were familiar with this evil. I think you allude to the transverse furrows on the forehead as a protection against sweat; but remember that these incessantly appear on the foreheads of baboons.
P.S.--I have been greatly pleased by the notices in the ”Nation.”
LETTER 268. TO A. WEISMANN. Down, May 1st, 1875.
I did not receive your essay for some days after your very kind letter, and I read german so slowly that I have only just finished it. (268/1.
”Studien zur Descendenz-Theorie” I. ”Ueber den Saison-Dimorphismus,”
1875. The fact was previously known that two forms of the genus Vanessa which had been considered to be distinct species are only SEASONAL forms of the same species--one appearing in spring, the other in summer. This remarkable relations.h.i.+p forms the subject of the essay.) Your work has interested me greatly, and your conclusions seem well established. I have long felt much curiosity about season-dimorphism, but never could form any theory on the subject. Undoubtedly your view is very important, as bearing on the general question of variability. When I wrote the ”Origin” I could not find any facts which proved the direct action of climate and other external conditions. I long ago thought that the time would soon come when the causes of variation would be fully discussed, and no one has done so much as you in this important subject. The recent evidence of the difference between birds of the same species in the N.
and S. United States well shows the power of climate. The two s.e.xes of some few birds are there differently modified by climate, and I have introduced this fact in the last edition of my ”Descent of Man.” (268/2.
”Descent of Man,” Edition II. (in one volume), page 423. Allen showed that many species of birds are more strongly coloured in the south of the United States, and that sometimes one s.e.x is more affected than the other. It is this last point that bears on Weismann's remarks (loc.
cit., pages 44, 45) on Pieris napi. The males of the alpine-boreal form bryoniae hardly differ from those of the German form (var. vernalis), while the females are strikingly different. Thus the character of secondary s.e.xual differences is determined by climate.) I am, therefore, fully prepared to admit the justness of your criticism on s.e.xual selection of lepidoptera; but considering the display of their beauty, I am not yet inclined to think that I am altogether in error.
What you say about reversion (268/3. For instance, the fact that reversion to the primary winter-form may be produced by the disturbing effect of high temperature (page 7).) being excited by various causes, agrees with what I concluded with respect to the remarkable effects of crossing two breeds: namely, that anything which disturbs the const.i.tution leads to reversion, or, as I put the case under my hypothesis of pangenesis, gives a good chance of latent gemmules developing. Your essay, in my opinion, is an admirable one, and I thank you for the interest which it has afforded me.
P.S. I find that there are several points, which I have forgotten. Mr.
Jenner Weir has not published anything more about caterpillars, but I have written to him, asking him whether he has tried any more experiments, and will keep back this letter till I receive his answer.
Mr. Riley of the United States supports Mr. Weir, and you will find reference to him and other papers at page 426 of the new and much-corrected edition of my ”Descent of Man.” As I have a duplicate copy of Volume I. (I believe Volume II. is not yet published in german) I send it to you by this post. Mr. Belt, in his travels in Nicaragua, gives several striking cases of conspicuously coloured animals (but not caterpillars) which are distasteful to birds of prey: he is an excellent observer, and his book, ”The Naturalist in Nicaragua,” very interesting.
I am very much obliged for your photograph, which I am particularly glad to possess, and I send mine in return.
I see you allude to Hilgendorf's statements, which I was sorry to see disputed by some good German observer. Mr. Hyatt, an excellent palaeontologist of the United States, visited the place, and likewise a.s.sured me that Hilgendorf was quite mistaken. (268/4. See Letters 252-7.)
I am grieved to hear that your eyesight still continues bad, but anyhow it has forced your excellent work in your last essay.
May 4th. Here is what Mr. Weir says:--
”In reply to your inquiry of Sat.u.r.day, I regret that I have little to add to my two communications to the 'Entomological Society Transactions.'
”I repeated the experiments with gaudy caterpillars for years, and always with the same results: not on a single occasion did I find richly coloured, conspicuous larvae eaten by birds. It was more remarkable to observe that the birds paid not the slightest attention to gaudy caterpillars, not even when in motion,--the experiments so thoroughly satisfied my mind that I have now given up making them.”
LETTER 269. TO LAWSON TAIT.
(269/1. The late Mr. Lawson Tait wrote to Mr. Darwin (June 2nd, 1875): ”I am watching a lot of my mice from whom I removed the tails at birth, and I am coming to the conclusion that the essential use of the tail there is as a recording organ--that is, they record in their memories the corners they turn and the height of the holes they pa.s.s through by touching them with their tails.” Mr. Darwin was interested in the idea because ”some German sneered at Natural Selection and instanced the tails of mice.”)
June 11th, 1875.