Charles Darwin and his incredible study of Earth Worms

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.

Manner in which worms seize objects--Their power of suction--The instinct of plugging up the mouths of their burrows--Stones piled over the burrows--The advantages thus gained--Intelligence shown by worms in their manner of plugging up their burrows--Various kinds of leaves and other objects thus used--Triangles of paper--Summary of reasons for believing that worms exhibit some intelligence-- Means by which they excavate their burrows, by pushing away the earth and swallowing it--Earth also swallowed for the nutritious matter which it contains--Depth to which worms burrow, and the construction of their burrows--Burrows lined with castings, and in the upper part with leaves--The lowest part paved with little stones or seeds--Manner in which the castings are ejected--The collapse of old burrows--Distribution of worms--Tower-like castings in Bengal--Gigantic castings on the Nilgiri Mountains--Castings ejected in all countries.

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 given time if uniformly spread out--The slow rate at which mould can increase to a great thickness--Conclusion.

The accumulation of rubbish on the sites of great cities independent of the action of worms--The burial of a Roman villa at Abinger--The floors and walls penetrated by worms--Subsidence of a modern pavement--The buried pavement at Beaulieu Abbey--Roman villas at Chedworth and Brading--The remains of the Roman town at Silchester--The nature of the debris by which the remains are covered--The penetration of the tesselated floors and walls by worms--Subsidence of the floors--Thickness of the mould--The old Roman city of Wroxeter--Thickness of the mould--Depth of the foundations of some of the Buildings--Conclusion.

Evidence of the amount of denudation which the land has undergone-- Sub-aerial denudation--The deposition of dust--Vegetable mould, its dark colour and 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 mill-stones-- The levigated state of the castings--Fragments of brick in the castings over ancient buildings well rounded. The triturating power of worms not quite insignificant under a geological point of view.

Denudation aided by recently ejected castings flowing down inclined grass-covered surfaces--The amount of earth which annually flows downwards--The effect of tropical rain on worm castings--The finest particles of earth washed completely away from castings--The disintegration of dried castings into pellets, and their rolling down inclined surfaces--The formation of little ledges on hill- sides, in part due to the accumulation of disintegrated castings-- Castings blown to leeward over level land--An attempt to estimate the amount thus blown--The degradation of ancient encampments and tumuli--The preservation of the crowns and furrows on land anciently ploughed--The formation and amount of mould over the Chalk formation.

Summary of the part which worms have played in the history of the world--Their aid in the disintegration of rocks--In the denudation of the land--In the preservation of ancient remains--In the preparation of the soil for the growth of plants--Mental powers of worms--Conclusion

Back Home