I have seen several burrows in undisturbed sand
thus lined at a depth of 4 ft. 6 in.; and others close to the
surface thus lined in recently dug ground. The walls of fresh
burrows are often dotted with little globular pellets of voided
earth, still soft and viscid; and these, as it appears, are spread
out on all sides by the worm as it travels up or down its burrow.
The lining thus formed becomes very compact and smooth when nearly
dry, and closely fits the worm's body. The minute reflexed
bristles which project in rows on all sides from the body, thus
have excellent points of support; and the burrow is rendered well
adapted for the rapid movement of the animal. The lining appears
also to strengthen the walls, and perhaps saves the worm's body
from being scratched. I think so because several burrows which
passed through a layer of sifted coal-cinders, spread over turf to
a thickness of 1.5 inch, had been thus lined to an unusual
thickness. In this case the worms, judging from the castings, had
pushed the cinders away on all sides and had not swallowed any of
them. In another place, burrows similarly lined, passed through a
layer of coarse coal-cinders, 3.5 inches in thickness. We thus see
that the burrows are not mere excavations, but may rather be
compared with tunnels lined with cement.
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