sake of lining the upper part or mouth.

When worms cannot obtain leaves, petioles, sticks, &c., with which
to plug up the mouths of their burrows, they often protect them by
little heaps of stones; and such heaps of smooth rounded pebbles
may frequently be seen on gravel-walks. Here there can be no
question about food. A lady, who was interested in the habits of
worms, removed the little heaps of stones from the mouths of
several burrows and cleared the surface of the ground for some
inches all round. She went out on the following night with a
lantern, and saw the worms with their tails fixed in their burrows,
dragging the stones inwards by the aid of their mouths, no doubt by
suction. "After two nights some of the holes had 8 or 9 small
stones over them; after four nights one had about 30, and another
34 stones." {29} One stone--which had been dragged over the
gravel-walk to the mouth of a burrow weighed two ounces; and this
proves how strong worms are. But they show greater strength in
sometimes displacing stones in a well-trodden gravel-walk; that
they do so, may be inferred from the cavities left by the displaced
stones being exactly filled by those lying over the mouths of
adjoining burrows, as I have myself observed.

Work of this kind is usually performed during the night; but I have
occasionally known objects to be drawn into the burrows during the
day. What advantage the worms derive from plugging up the mouths
of their burrows with leaves, &c., or from piling stones over them,
is doubtful. They do not act in this manner at the times when they
eject much earth from their burrows; for their castings then serve
to cover the mouths. When gardeners wish to kill worms on a lawn,
it is necessary first to brush or rake away the castings from the