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1880 Circumnutating movements All Spring finishing M.S. of Power of Movement in Plants 1 then Proof Sheets Began in Autumn on Worms. Nov. 6th 1500 copies of Power of Movement sold at Murray's Sale 1 Movement in plants. All Spring...Murray's Sale] in blue ink. [59] [1880
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F1357
Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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fine texture largely due to the action of worms The disintegration of rocks by the humus-acids Similar acids apparently generated within the bodies of worms The action of these acids facilitated by the continued movement of the particles of earth A thick bed of mould checks the disintegration of the underlying soil and rocks Particles of stone worn or triturated in the gizzards of worms Swallowed stones serve as millstones The levigated state of the castings Fragments of brick in the castings
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F1357
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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already alluded to, which appeared in 1877. Before entering on details with respect to the castings, it will be advisable to give some account of the habits of worms from my own observations and from those of other naturalists. [page]
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F1357
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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fetched; for we thus attribute to the worm attention and some mental power, nevertheless I can see no reason to doubt the justice of the comparison. Although worms cannot be said to possess the power of vision, their sensitiveness to light enables them to distinguish between day and night; and they thus escape extreme danger from the many diurnal animals which prey on them. Their withdrawal into their burrows during the day appears, however, to have become an habitual action; for worms kept in
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F1357
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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breath whilst I chewed some tobacco, and while a pellet of cotton-wool with a few drops of mille-fleurs perfume or of acetic acid was kept in my mouth. Pellets of cotton-wool soaked in tobacco juice, and in millefleurs perfume, and in paraffin, were held with pincers and were waved about within two or three inches of several worms, but they took no notice. On one or two occasions, however, when acetic acid had been placed on the pellets, the worms appeared a little uneasy, and this was probably
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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On two occasions, however, the surface was well watered, and was thus rendered some-what compact. After the bits of cabbage and onion had been removed, I looked beneath them to see whether the worms had accidentally come up from below, but there was no sign of a burrow; and twice the buried objects were laid on pieces of tin-foil which were not in the least displaced. It is of course possible that the worms whilst moving about on the surface of the ground, with their tails affixed within their
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F1357
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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seen on one occasion, when a large worm lying beneath a flaccid cabbage leaf tried to drag it away; for the surface of the leaf directly over the end of the worms body became deeply pitted. On another occasion a worm suddenly lost its hold on a flat leaf; and the anterior end of the body was momentarily seen to be cup-formed. Worms can attach themselves to an object beneath water in the same manner; and I saw one thus dragging away a submerged slice of an onion-bulb. The edges of fresh or
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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I collected a handful of petioles lying loose on the ground close to some plugged-up burrows, where the surface was thickly strewed with other petioles which apparently had never been touched by worms; and 14 out of 47 (i.e. nearly one-third), after having had their bases gnawed had been pushed out of the burrows and were now lying on the ground. From these several facts we may conclude that worms draw in some petioles of the ash by the base to serve as food, and others by the tip to plug up
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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petioles of the Clematis could certainly have been drawn in with equal ease by the base and apex; yet three times and in certain cases five times as many were drawn in by the apex as by the base. It might have been thought that the foot-stalks of leaves would have tempted the worms as a convenient handle; yet they are not largely used, except when the base of the blade is narrower than the apex. A large number of the petioles of the ash are drawn in by the base; but this part serves the worms as
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Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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choice does not appear to be determined by the divergence of the two needles, and the consequent advantage or necessity of drawing them into their burrows by the base. With respect to the triangles of paper, those which had been drawn in by the apex rarely had their bases creased or dirty; and this shows that the worms had not often first tried to drag them in by this end. If worms are able to judge, either before drawing or after having drawn an object close to the mouths of their burrows
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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between the sides of the pot and the earth, which had been moderately pressed down. On a third occasion three large worms and a small one were placed on loose mould well mixed with fine sand and firmly pressed down, and they all disappeared, except the tail of one, in 35 minutes. On a fourth occasion six large worms were placed on argillaceous mud mixed with sand firmly pressed down, and they disappeared, except the extreme tips of the tails of two of them, in 40 minutes. In none of these cases, did
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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and every morning many fresh castings were seen; but not a single leaf was drawn into these burrows. These castings from their blackness and from the nature of the subsoil could not have been brought up from a greater depth than 6 or 8 inches. On what could these worms have subsisted during this whole time, if not on matter contained in the black earth? On the other hand, whenever a large number of leaves are drawn into the burrows, the worms seem to subsist chiefly on them, for few earth
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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the exterior surfaces of the towers in search of leaves; and had they done so, tracks would almost certainly have been left on the upper part whilst it remained soft. It does not, however, follow that these worms do not draw leaves into their burrows during some other season of the year, at which time they would not build up their towers. From the several foregoing cases, it can hardly be doubted that worms swallow earth, not only for the sake of making their burrows, but for obtaining food
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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prevented the retreat of the worms into their burrows; and these structures would have resembled traps armed with converging points of wire, rendering the ingress of an animal easy and its egress difficult or impossible. The skill shown by these worms is noteworthy and is the more remarkable, as the Scotch pine is not a native of this district. After having examined these burrows made by worms in confinement, I looked at those in a flower-bed near some Scotch pines. These had all been plugged up in
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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abound in Iceland, and are known to exist in the West Indies, St. Helena, Madagascar, New Caledonia and Tahiti. In the Antarctic regions, worms from Kerguelen Land have been described by Ray Lankester; and I found them in the Falkland Islands. How they reach such isolated islands is at present quite unknown. They are easily killed by salt-water, and it does not appear probable that young worms or their egg-capsules could be carried in earth adhering to the feet or beaks of land-birds. Moreover
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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CHAPTER III. THE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE SURFACE. Rate at which various objects strewed on the surface of grass-fields are covered up by the castings of worms The burial of a paved path The slow subsidence of great stones left on the surface The number of worms which live within a given space The weight of earth ejected from a burrow, and from all the burrows within a given space The thickness of the layer of mould which the castings on a given space would form within a
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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especially if we bear in mind that a good deal of the finest earth would have been washed by heavy rain from the castings ejected on the sloping border down to the level of the field. Some fresh castings were seen close to the stone. Nevertheless, on digging a large hole to a depth of 18 inches where the stone had lain, only two worms and a few burrows were seen, although the soil was damp and seemed favourable for worms. There were some large colonies of ants beneath the stone, and possibly since their
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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Place was sandy soil including many bits of rock, and at Stonehenge, chalk-rubble with broken flints; considering, also, the presence of the turf-covered sloping border of mould round the great fragments of stone at both these places, their sinking does not appear to have been sensibly aided by their weight, though this was considerable.* On the number of worms which live within a given space. We will now show, firstly, what a vast number of worms live unseen by us beneath our feet, and
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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open hands, which was penetrated by seven burrows, as large as goose-quills. Weight of the earth ejected from a single burrow, and from all the burrows within a given space. With respect to the weight of the earth daily ejected by worms, Hensen found that it amounted, in the case of some worms which he kept in confinement, and which he appears to have fed with leaves, to only 0 5 gram, or less than 8 grains per diem. But a very much larger amount must be ejected by worms in their natural state, at
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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which worms ever burrow, were there not other opposing agencies at work which carry away to a lower level some of the finest earth which is continually being brought to the surface by worms. How great a thickness vegetable mould ever attains, I have not had good opportunities for observing; but in the next chapter, when we consider the burial of ancient buildings, some facts will be given on this head. In the two last chapters we shall see that the soil is actually increased, though only to a
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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cleared. On the previous night there had been some heavy rain, which washed the surface clean, and now the mouths of forty burrows were counted. Parts of the concrete were seen to be solid, and had never been penetrated by worms, and here the rainwater lodged. Sept. 5th. Tracks of worms, made during the previous night, could be seen on the surface of the floor, and five or six vermiform castings had been thrown up. These were defaced. Sept. 12th. During the last six days, the worms have not been
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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up by the worms with their castings, as soon as they were able to penetrate the wall. Rain-water, oozing down the burrows would also carry fine dark-coloured particles into every crevice. Mr. Joyce was at first very sceptical about the amount of work which I attributed to worms; but he ends his notes with reference to the last-mentioned wall by saying, This case caused me more surprise and brought more conviction to me than any other. I should have said, and did say, that it was quite
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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neutralise the acids thus generated; for the digestive fluid of worms will not act unless it be alkaline. As the contents of the upper part of their intestines are acid, the acidity can hardly be due to the presence of uric acid. We may therefore conclude that the acids in the alimentary canal of worms are formed during the digestive process; and that probably they are nearly of the same nature as those in ordinary humus. The latter are well known to have the power of de-oxidising or dissolving
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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through their alimentary canals. With worms living in a state of nature, it is of course impossible to know how much the fragments may have been worn before they were swallowed. It is, however, clear that worms do not habitually select already rounded particles, for sharply angular bits of flint and of other hard rocks were often found in their gizzards or intestines. On three occasions sharp spines from the stems of rose-bushes were thus found. Worms kept in confinement repeatedly swallowed
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. London: John Murray.
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Bridgman, Mr., on worms eating leaves of a Phlox, 33 Buckman, on grasses profiting by being rolled, 10 Burial of the remains of ancient buildings by worms, 176 Burrows, depth of, 109 direction of, on a slope, 270 excavation of, 98 lined with black earth, 111 lined with leaves, 112 mouths of, worms lie motionless near, 15 old, their collapse, 118 plugged up, 58 terminating in a small chamber, often lined with stones or seeds, 114 Calciferous glands, 17, 43 Cannibal worms, 36 Carnagie, Mr
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Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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THE FORMATION OF VEGETABLE MOULD, THROUGH THE ACTION OF WORMS, WITH OBSERVATIONS ON THEIR HABITS. BY CHARLES DARWIN, LLD., F.R.S. WITH ILLUSTRATIONS. FIFTH THOUSAND (CORRECTED). LONDON: JOHN MURRAY, ALBEMARLE STREET. 1881. The right of Translation is reserved. [page ii
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Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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fine texture largely due to the action of worms The disintegration of rocks by the humus-acids Similar acids apparently generated within the bodies of worms The action of these acids facilitated by the continued movement of the particles of earth A thick bed of mould checks the disintegration of the underlying soil and rocks Particles of stone worn or triturated in the gizzards of worms Swallowed stones serve as millstones The levigated state of the castings Fragments of brick in the castings
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Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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already alluded to, which appeared in 1877. Before entering on details with respect to the castings, it will be advisable to give some account of the habits of worms from my own observations and from those of other naturalists. [page]
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F1361
Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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fetched; for we thus attribute to the worm attention and some mental power, nevertheless I can see no reason to doubt the justice of the comparison. Although worms cannot be said to possess the power of vision, their sensitiveness to light enables them to distinguish between day and night; and they thus escape extreme danger from the many diurnal animals which prey on them. Their withdrawal into their burrows during the day appears, however, to have become an habitual action; for worms kept in
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F1361
Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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beneath them to see whether the worms had accidentally come up from below, but there was no sign of a burrow; and twice the buried objects were laid on pieces of tin-foil which were not in the least displaced. It is of course possible that the worms whilst moving about on the surface of the ground, with their tails affixed within their burrows, may have poked their heads into the places where the above objects were buried; but I have never seen worms acting in this manner. Some pieces of
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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sionally and very slightly nibbled. These latter four kinds of leaves do not differ in texture in a manner which could make them disagreeable to worms; they all have a strong taste, but so have the four first mentioned kinds of leaves; and the wide difference in the result must be attributed to a preference by the worms for one taste over another. Mental Qualities. There is little to be said on this head. We have seen that worms are timid. It may be doubted whether they suffer as much pain
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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this fluid serves to hasten their decay; but a large number of leaves were twice pulled out of the burrows of worms and kept for many weeks in a very moist atmosphere under a bell-glass in my study; and the parts which had been moistened by the worms did not decay more quickly in any plain manner than the other parts. When fresh leaves were given in the evening to worms kept in confinement and examined early on the next morning, therefore not many hours after they had been dragged into the burrows
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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have been known to contain as much as 72 per cent. of lime. Worms therefore would be liable to become charged with this earth, unless there were some special means for its excretion; and the calciferous glands are well adapted for this purpose. The worms which live in mould close over the chalk, often have their intestines filled with this substance, and their castings are almost white. Here it is evident that the supply of calcareous matter must be superabundant. Nevertheless with several
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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and this probably resulted from the humus acids being, as is known to be the case, easily decomposed. Five fresh castings from worms which lived in mould close over the chalk, were of a whitish colour and abounded with calcareous matter; and these were not in the least acid. This shows how effectually carbonate of lime neutralises the intestinal acids. When worms were kept in pots filled with fine ferruginous sand, it was manifest that the oxide of iron, with which the grains of silex were
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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seen on one occasion, when a large worm lying beneath a flaccid cabbage leaf tried to drag it away; for the surface of the leaf directly over the end of the worm's body became deeply pitted. On another occasion a worm suddenly lost its hold on a flat leaf; and the anterior end of the body was momentarily seen to be cup-formed. Worms can attach themselves to an object beneath water in the same manner; and I saw one thus dragging away a submerged slice of an onion-bulb. The edges of fresh or
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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probable explanation of the habit. But the plugging-up process may serve for all the above purposes. Whatever the motive may be, it appears that worms much dislike leaving the mouths of their burrows open. Nevertheless they will reopen them at night, whether or not they can afterwards close them. Numerous open burrows may be seen on recently-dug ground, for in this case the worms eject their castings in cavities left in the ground, or in the old burrows, instead of piling them over the mouths
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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leaves drawn into the burrows, no less than 16 were drawn in by the tips of the needles. These worms, however, worked in a careless or slovenly manner; for the leaves were often drawn in to only a small depth; sometimes they were merely heaped over the mouths of the burrows, and sometimes none were drawn in. I believe that this carelessness may be accounted for by the air of the room being warm, and the worms consequently not being anxious to plug up their holes effectually. Pots tenanted by worms
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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petioles of the Clematis could certainly have been drawn in with equal ease by the base and apex; yet three times and in certain cases five times as many were drawn in by the apex as by the base. It might have been thought that the foot-stalks of leaves would have tempted the worms as a convenient handle; yet they are not largely used, except when the base of the blade is narrower than the apex. A large number of the petioles of the ash are drawn in by the base; but this part serves the worms as
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F1361
Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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choice does not appear to be determined by the divergence of the two needles, and the consequent advantage or necessity of drawing them into their burrows by the base. With respect to the triangles of paper, those which had been drawn in by the apex rarely had their bases creased or dirty; and this shows that the worms had not often first tried to drag them in by this end. If worms are able to judge, either before drawing or after having drawn an object close to the mouths of their burrows
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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between the sides of the pot and the earth, which had been moderately pressed down. On a third occasion three large worms and a small one were placed on loose mould well mixed with fine sand and firmly pressed down, and they all disappeared, except the tail of one, in 35 minutes. On a fourth occasion six large worms were placed on argillaceous mud mixed with sand firmly pressed down, and they disappeared, except the extreme tips of the tails of two of them, in 40 minutes. In none of these cases, did
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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and every morning many fresh castings were seen; but not a single leaf was drawn into these burrows. These castings from their blackness and from the nature of the subsoil could not have been brought up from a greater depth than 6 or 8 inches. On what could these worms have subsisted during this whole time, if not on matter contained in the black earth? On the other hand, whenever a large number of leaves are drawn into the burrows, the worms seem to subsist chiefly on them, for few earth
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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the exterior surfaces of the towers in search of leaves; and had they done so, tracks would almost certainly have been left on the upper part whilst it remained soft. It does not, however, follow that these worms do not draw leaves into their burrows during some other season of the year, at which time they would not build up their towers. From the several foregoing cases, it can hardly be doubted that worms swallow earth, not only for the sake of making their burrows, but for obtaining food
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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prevented the retreat of the worms into their burrows; and these structures would have resembled traps armed with converging points of wire, rendering the ingress of an animal easy and its egress difficult or impossible. The skill shown by these worms is noteworthy and is the more remarkable, as the Scotch pine is not a native of this district. After having examined these burrows made by worms in confinement, I looked at those in a flower-bed near some Scotch pines. These had all been plugged up in
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Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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abound in Iceland, and are known to exist in the West Indies, St. Helena, Madagascar, New Caledonia and Tahiti. In the Antarctic regions, worms from Kerguelen Land have been described by Ray Lankester; and I found them in the Falkland Islands. How they reach such isolated islands is at present quite unknown. They are easily killed by salt-water, and it does not appear probable that young worms or their egg-capsules could be carried in earth adhering to the feet or beaks of land-birds. Moreover
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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CHAPTER III. THE AMOUNT OF FINE EARTH BROUGHT UP BY WORMS TO THE SURFACE. Rate at which various objects strewed on the surface of grass-fields are covered up by the castings of worms The burial of a paved path The slow subsidence of great stones left on the surface The number of worms which live within a given space The weight of earth ejected from a burrow, and from all the burrows within a given space The thickness of the layer of mould which the castings on a given space would form within a
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Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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sunk about 2 inches into the ground; more especially if we bear in mind that a good deal of the finest earth would have been washed by heavy rain from the castings ejected on the sloping border down to the level of the field. Some fresh castings were seen close to the stone. Nevertheless, on digging a large hole to a depth of 18 inches where the stone had lain, only two worms and a few burrows were seen, although the soil was damp and seemed favourable for worms. There were some large colonies of
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F1361
Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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lower level some of the finest earth which is continually being brought to the surface by worms. How great a thickness vegetable mould ever attains, I have not had good opportunities for observing; but in the next chapter, when we consider the burial of ancient buildings, some facts will be given on this head. In the two last chapters we shall see that the soil is actually increased, though only to a small degree, through the agency of worms; but their chief work is to sift the finer from the
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F1361
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Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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cleared. On the previous night there had been some heavy rain, which washed the surface clean, and now the mouths of forty burrows were counted. Parts of the concrete were seen to be solid, and had never been penetrated by worms, and here the rainwater lodged. Sept. 5th. Tracks of worms, made during the previous night, could be seen on the surface of the floor, and five or six vermiform castings had been thrown up. These were defaced. Sept. 12th. During the last six days, the worms have not been
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F1361
Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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up by the worms with their castings, as soon as they were able to penetrate the wall. Rain-water, oozing down the burrows would also carry fine dark-coloured particles into every crevice. Mr. Joyce was at first very sceptical about the amount of work which I attributed to worms; but he ends his notes with reference to the last-mentioned wall by saying, This case caused me more surprise and brought more conviction to me than any other. I should have said, and did say, that it was quite
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F1361
Book:
Darwin, C. R. 1881. The formation of vegetable mould, through the action of worms, with observations on their habits. fifth thousand (corrected), and with textual changes. London: John Murray.
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neutralise the acids thus generated; for the digestive fluid of worms will not act unless it be alkaline. As the contents of the upper part of their intestines are acid, the acidity can hardly be due to the presence of uric acid. We may therefore conclude that the acids in the alimentary canal of worms are formed during the digestive process; and that probably they are nearly of the same nature as those in ordinary mould or humus. The latter are well known to have the power of de-oxidising or
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