Search for a command to run...
Nature of the sites inhabited-Can live long under water -Nocturnal-Wander about at night-Often lie close to the mouths of their burrows, and are thus destroyed in large numbers by birds-Structure-Do not possess eyes, but can distinguish between light and darkness-Retreat rapidly when brightly illuminated, not by a reflex action-Power of attention -Sensitive to heat and cold -Completely deaf -Sensitive to vibrations and to touch -Feeble power of smell-Taste -Mental qualities -Nature of food-Omnivorous-Digestion -Leaves before being swallowed, moistened with a fluid of the nature of the pancreatic secretion -Extra-stomachal digestion -Calciferous glands, structure of-Calcareous concretions formed in the anterior pair of glands The calcareous matter primarily an excretion, but secondarily serves to neutralise the acids generated during the digestive process.Earth-worms are distributed throughout the world under the form of a few genera, which externally are closely similar to one another.The British species of Lumbricus have never been carefully monographed; but we may judge of their probable number from those inhabiting neighbouring countries.In Scan- dinavia there are eight species, according to Chap.I. SITES INHABITED.9 Eisen ;* but two of these rarely burrow in the ground, and one inhabits very wet places or even lives under the water.We are here concerned only with the kinds whicli bring up earth to the surface in the form of cast- ings.Hoffmeister says that the species in Germany are not well known, but gives the same number as Eisen, together with some strongly marked varieties.fEarth-worms abound in England in many different stations.Their castings may be seen in extraordinary numbers on commons and chalk-downs, so as almost to cover the whole surface, where the soil is poor and the grass short and thin.But they are almost or quite as numerous in some of the London parks, where the grass grows well and the soil appears rich.Even on the same field worms are much more frequent in some places than in others, without any visible difference in the nature of the soil.They abound in paved court-yards close to houses ; and an instance will be given in which they had * 'Bidrag till Skandinaviens Oligochastfauna,' 1871.t 'Die bis jetzt bekannten Arten aus der Familie der Regen- wtirmer,' 1845.HABITS OF WORMS.Chap.I. burrowed through the floor of a very damp cellar.I have seen worms in black peat in a boggy field ; but they are extremely rare, or quite absent in the drier, brown, fibrous peat, which is so much valued by gardeners.On dry, sandy or gravelly tracks, where heath with some gorse, ferns, coarse grass, moss and lichens alone grow, hardly any worms can be found.But in many parts of England, wherever a path crosses a heath, its surface becomes covered with a fine short sward.Whether this change of vegetation is due to the taller plants being killed by the occasional trampling of man and animals, or to the soil being occasionally manured by the droppings from animals, I do not know.*On such grassy paths worm-castings may often be seen.On a heath in Surrey, which was carefully examined, there were only a few castings on these paths, where they were much inclined ; * There is even some reason to believe that pressure is actually favourable to the growth of grasses, for Professor Buckman, who made many observations on their growth in the experimental gardens of the Royal Agricultural College, remarks (' Gardeners' Chronicle,' 1854, p. 619) : " Another circumstance in the cultiva- tion of grasses in the separate form or small patches, is the impossibility of rolling or treading them firmly, withoui which no pasture can continue good."Chap.I.SITES INHABITED.11 but on the more level parts, where a bed of fine earth had been washed down from the steeper parts and had accumulated to a thick- ness of a few inches, worm-castings abounded.These spots seemed to be overstocked wdth worms, so that they had been compelled to spread to a distance of a few feet from the grassy paths, and here their castings had been thrown up among the heath ; but beyond this limit, not a single casting could be found.A layer, though a thin one, of fine earth, which probably long retains some moisture, is in all cases, as I believe, necessary for their existence ; and the mere compression of the soil appears to be in some degree favourable to them, for they often abound in old gravel walks, and in foot-paths across fields.Beneath large trees few castings can be found during certain seasons of the year, and this is apparently due to the moisture having been sucked out of the ground by the innu- merable roots of the trees ; for such places may be seen covered with castings after the heavy autumnal rains.Although most cop- pices and woods support many worms, yet in a forest of tall and ancient beech-trees in Knole 12 HABITS OF WORMS.Chap.I.Park, where the ground beneath was bare of all vegetation, not a single casting could be found over wide spaces, even during the autumn.Nevertheless, castings were abun- dant on some grass-covered glades and in- dentations which penetrated this forest.On the mountains of North Wales and on the Alps, worms, as I have been informed, are in most places rare ; and this may perhaps be due to the close proximity of the subjacent rocks, into which worms cannot .burrow during the winter so as to escape being frozen.Dr. McIntosh, however, found worm-castings at a height of 1500 feet on Schiehallion in Scotland.They are numerous on some hills near Turin at from 2000 to 3000 feet above the sea, and at a great altitude on the Nilgiri Mountains in South India and on the Himalaya.Earth-worms must he considered as terres- trial animals, though they are still in one sense semi-aquatic, like the other members of the great class of annelids to which they belong.M. Perrier found that their ex- posure to the dry air of a room for only a single night was fatal to them.On the Chap.I.NOCTURNAL.13 other hand he kept several large worms alive for nearty four months, completely submerged in water.*During the summer when the ground is dry, they penetrate to a consider- able depth and cease to work, as they do during the winter when the ground is frozen.Worms are nocturnal in their habits, and at night may be seen crawling about in large numbers, but usually with their tails still inserted in their burrows.By the expansion of this part of their bodies, and with the help of the short, slightly reflexed bristles, with which their bodies are armed, they hold so fast that they can seldom be dragged out of the ground without being torn into pieces.fDuring the day they remain in their burrows, except at the pairing season, when those which inhabit adjoining burrows expose the greater part of their bodies for an hour or two in the early morning.Sick * I shall have occasion often to refer to M. Perrier's admirable