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- More Letters of Charles Darwin Volume II - 3/133 -
What a case it is. Palms, screw-pines, four snakes--not one being in main island--lizards, insects, and not one land bird. But, above everything, such a proportion of individual monocotyledons! The conditions do not seem very different from the Tuff Galapagos Island, but, as far as I remember, very few monocotyledons there. Then, again, the island seems to have been elevated. I wonder much whether it stands out in the line of any oceanic current, which does not so forcibly strike the main island? But why, oh, why should so many monocotyledons have come there? or why should they have survived there more than on the main island, if once connected? So, again, I cannot conceive that four snakes should have become extinct in Mauritius and survived on Round Island. For a moment I thought that Mauritius might be the newer island, but the enormous degradation which the outer ring of rocks has undergone flatly contradicts this, and the marine remains on the summit of Round Island indicate the island to be comparatively new--unless, indeed, they are fossil and extinct marine remains. Do tell me what you think. There never was such an enigma. I rather lean to separate immigration, with, of course, subsequent modification; some forms, of course, also coming from Mauritius. Speaking of Mauritius reminds me that I was so much pleased the day before yesterday by reading a review of a book on the geology of St. Helena, by an officer who knew nothing of my hurried observations, but confirms nearly all that I have said on the general structure of the island, and on its marvellous denudation. The geology of that island was like a novel.
LETTER 387. TO A. BLYTT. Down, March 28th, 1876.
(387/1. The following refers to Blytt's "Essay on the Immigration of the Norwegian Flora during Alternating Rainy and Dry Periods," Christiania, 1876.)
I thank you sincerely for your kindness in having sent me your work on the "Immigration of the Norwegian Flora," which has interested me in the highest degree. Your view, supported as it is by various facts, appears to me the most important contribution towards understanding the present distribution of plants, which has appeared since Forbes' essay on the effects of the Glacial Period.
LETTER 388. TO AUG. FOREL. Down, June 19th, 1876.
I hope you will allow me to suggest an observation, should any opportunity occur, on a point which has interested me for many years--viz., how do the coleoptera which inhabit the nests of ants colonise a new nest? Mr. Wallace, in reference to the presence of such coleoptera in Madeira, suggests that their ova may be attached to the winged female ants, and that these are occasionally blown across the ocean to the island. It would be very interesting to discover whether the ova are adhesive, and whether the female coleoptera are guided by instinct to attach them to the female ants (388/1. Dr. Sharp is good enough to tell us that he is not aware of any such adaptation. Broadly speaking, the distribution of the nest-inhabiting beetles is due to co-migration with the ants, though in some cases the ants transport the beetles. Sitaris and Meloe are beetles which live "at the expense of bees of the genus Anthophora." The eggs are laid not in but near the bees' nest; in the early stage the larva is active and has the instinct to seize any hairy object near it, and in this way they are carried by the Anthophora to the nest. Dr. Sharp states that no such preliminary stage is known in the ant's-nest beetles. For an account of Sitaris and Meloe, see Sharp's "Insects," II., page 272.); or whether the larvae pass through an early stage, as with Sitaris or Meloe, or cling to the bodies of the females. This note obviously requires no answer. I trust that you continue your most interesting investigations on ants.
(PLATE: MR. A.R. WALLACE, 1878. From a photograph by Maull & Fox.)
LETTER 389. TO A.R. WALLACE.
(389/1. Published in "Life and Letters," III., page 230.)
(389/2. The following five letters refer to Mr. Wallace's "Geographical Distribution of Animals," 1876.)
[Hopedene] (389/3. Mr. Hensleigh Wedgwood's house in Surrey.), June 5th, 1876.
I must have the pleasure of expressing to you my unbounded admiration of your book (389/4. "Geographical Distribution," 1876.), though I have read only to page 184--my object having been to do as little as possible while resting. I feel sure that you have laid a broad and safe foundation for all future work on Distribution. How interesting it will be to see hereafter plants treated in strict relation to your views; and then all insects, pulmonate molluscs and fresh-water fishes, in greater detail than I suppose you have given to these lower animals. The point which has interested me most, but I do not say the most valuable point, is your protest against sinking imaginary continents in a quite reckless manner, as was stated by Forbes, followed, alas, by Hooker, and caricatured by Wollaston and [Andrew] Murray! By the way, the main impression that the latter author has left on my mind is his utter want of all scientific judgment. I have lifted up my voice against the above view with no avail, but I have no doubt that you will succeed, owing to your new arguments and the coloured chart. Of a special value, as it seems to me, is the conclusion that we must determine the areas, chiefly by the nature of the mammals. When I worked many years ago on this subject, I doubted much whether the now-called Palaearctic and Nearctic regions ought to be separated; and I determined if I made another region that it should be Madagascar. I have, therefore, been able to appreciate your evidence on these points. What progress Palaeontology has made during the last twenty years! but if it advances at the same rate in the future, our views on the migration and birthplace of the various groups will, I fear, be greatly altered. I cannot feel quite easy about the Glacial period, and the extinction of large mammals, but I must hope that you are right. I think you will have to modify your belief about the difficulty of dispersal of land molluscs; I was interrupted when beginning to experimentise on the just hatched young adhering to the feet of ground-roosting birds. I differ on one other point--viz. in the belief that there must have existed a Tertiary Antarctic continent, from which various forms radiated to the southern extremities of our present continents. But I could go on scribbling forever. You have written, as I believe, a grand and memorable work, which will last for years as the foundation for all future treatises on Geographical Distribution.
P.S.--You have paid me the highest conceivable compliment, by what you say of your work in relation to my chapters on distribution in the "Origin," and I heartily thank you for it.
LETTER 390. FROM A.R. WALLACE TO CHARLES DARWIN. The Dell, Grays, Essex, June 7th, 1876.
Many thanks for your very kind letter. So few people will read my book at all regularly, that a criticism from one who does so will be very welcome. If, as I suppose, it is only to page 184 of Volume I. that you have read, you cannot yet quite see my conclusions on the points you refer to (land molluscs and Antarctic continent). My own conclusion fluctuated during the progress of the book, and I have, I know, occasionally used expressions (the relics of earlier ideas) which are not quite consistent with what I say further on. I am positively against any Southern continent as uniting South America with Australia or New Zealand, as you will see at Volume I., pages 398-403, and 459-66. My general conclusions as to distribution of land mollusca are at Volume II., pages 522-9. (390/1. "Geographical Distribution" II., pages 524, 525. Mr. Wallace points out that "hardly a small island on the globe but has some land-shells peculiar to it"--and he goes so far as to say that probably air-breathing mollusca have been chiefly distributed by air- or water-carriage, rather than by voluntary dispersal on the land.) When you have read these passages, and looked at the general facts which lead to them, I shall be glad to hear if you still differ from me.
Though, of course, present results as to the origin and migrations of genera of mammals will have to be modified owing to new discoveries, I cannot help thinking that much will remain unaffected, because in all geographical and geological discoveries the great outlines are soon reached, the details alone remain to be modified. I also think much of the geological evidence is now so accordant with, and explanatory of, Geographical Distribution, that it is prima facie correct in outline. Nevertheless, such vast masses of new facts will come out in the next few years that I quite dread the labour of incorporating them in a new edition.
I hope your health is improved; and when, quite at your leisure, you have waded through my book, I trust you will again let me have a few lines of friendly criticism and advice.
LETTER 391. TO A.R. WALLACE. Down, June 17th, 1876.
I have now finished the whole of Volume I., with the same interest and admiration as before; and I am convinced that my judgment was right and that it is a memorable book, the basis of all future work on the subject. I have nothing particular to say, but perhaps you would like to hear my impressions on two or three points. Nothing has struck me more than the admirable and convincing manner in which you treat Java. To allude to a very trifling point, it is capital about the unadorned head of the Argus- pheasant. (391/1. See "Descent of Man," Edition I., pages 90 and 143, for drawings of the Argus pheasant and its markings. The ocelli on the wing feathers were favourite objects of Mr. Darwin, and sometimes formed the subject of the little lectures which on rare occasions he would give to a visitor interested in Natural History. In Mr. Wallace's book the meaning of the ocelli comes in by the way, in the explanation of Plate IX., "A Malayan Forest with some of its peculiar Birds." Mr. Wallace (volume i., page 340) points out that the head of the Argus pheasant is, during the display of the wings, concealed from the view of a spectator in front, and this accounts for the absence of bright colour on the head--a most unusual point in a pheasant. The case is described as a "remarkable confirmation of Mr. Darwin's views, that gaily coloured plumes are developed in the male bird for the purpose of attractive display." For the difference of opinion between the two naturalists on the broad question of coloration see "Life and Letters," III., page 123. See Letters 440-453.) How plain a thing is, when it is once pointed out! What a wonderful case is that of Celebes: I am glad that you have slightly modified your views with respect to Africa. (391/2. "I think this must refer to the following passage in 'Geog. Dist. of Animals,' Volume I., pages 286-7. 'At this period (Miocene) Madagascar was no doubt united with Africa, and helped to form a great southern continent which must at one time have extended eastward as far as Southern India and Ceylon; and over the whole of this the lemurine type no doubt prevailed.' At the time this was written I had not paid so much attention to islands, and in my "Island Life" I have given ample reasons for my belief that the evidence of extinct animals does not require any direct connection between Southern India and Africa."--Note by Mr. Wallace.) And this leads me to say that I cannot swallow the so-called continent of Lemuria--i.e., the direct connection of Africa and Ceylon. (391/3. See "Geographical Distribution," I., page 76. The name Lemuria was proposed by Mr. Sclater for an imaginary submerged continent extending from Madagascar to Ceylon and Sumatra. Mr. Wallace points out that if we confine ourselves to facts Lemuria is reduced to Madagascar, which he makes a subdivision of
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