ly
favorable for their decomposition and disintegration. Moreover, the
particles of the softer rocks suffer some amount of mechanical
trituration in the muscular gizzards of worms, in which small stones
serve as mill-stones....

Archaeologists ought to be grateful to worms, as they protect and
preserve for an indefinitely long period every object, not liable to
decay, which is dropped on the surface of the land, by burying it
beneath their castings. Thus, also, many elegant and curious tesselated
pavements and other ancient remains have been preserved; though no doubt
the worms have in these cases been largely aided by earth washed and
blown from the adjoining land, especially when cultivated. The old
tesselated pavements have, however, often suffered by having subsided
unequally from being unequally undermined by the worms. Even old massive
walls may be undermined and subside; and no building is in this respect
safe, unless the foundations lie six or seven feet beneath the surface,
at a depth at which worms cannot work. It is probable that many
monoliths and some old walls have fallen down from having been
undermined by worms.

Worms prepare the ground in an excellent manner for the growth of
fibrous-rooted plants and for seedlings of all kinds. They periodically
expose the mould to the air, and sift it so that no stones larger than
the particles which they can swallow are left in it. They mingle the
whole intimately together, like a gardener who prepares fine soil for
his choicest plants. In this state it is well fitted to retain moisture
and to absorb all soluble substances, as well as for the process of
nitrification. The bones of dead animals, the harder parts of insects,
the shells of land-molluscs, leaves, twigs, etc., are before long all
buried beneath the accumulated castings of worms, and are thus brought
in a more or less decayed state within reach of the roots of plants.
Worms likewise drag an infinite number of dead leaves and other parts of
plants into their burrows, partly for the sake of plugging them up and
partly as food.

The leaves which are dragged into the burrows as food, after being
torn into the finest shreds, partially digested, and saturated with
the intestinal secretions, are commingled with much earth. This
earth forms the dark-colored, rich humus which almost everywhere
covers the surface of the land with a fairly well-defined layer or
mantle. Von Hensen placed two worms in a vessel eig