The mouths of the burrow are in addition often lined with leaves;
and this is an instinct distinct from that of plugging them up, and
does not appear to have been hitherto noticed. Many leaves of the
Scotch-fir or pine (Pinus sylvestris) were given to worms kept in
confinement in two pots; and when after several weeks the earth was
carefully broken up, the upper parts of three oblique burrows were
found surrounded for lengths of 7, 4, and 3.5 inches with pine-
leaves, together with fragments of other leaves which had been
given the worms as food. Glass beads and bits of tile, which had
been strewed on the surface of the soil, were stuck into the
interstices between the pine-leaves; and these interstices were
likewise plastered with the viscid castings voided by the worms.
The structures thus formed cohered so well, that I succeeded in
removing one with only a little earth adhering to it. It consisted
of a slightly curved cylindrical case, the interior of which could
be seen through holes in the sides and at either end. The pine-
leaves had all been drawn in by their bases; and the sharp points
of the needles had been pressed into the lining of voided earth.
Had this not been effectually done, the sharp points would have
prevented the retreat of the worms into their burrows; and these
structures would have resembled traps armed with converging points
of wire, rendering the ingress of an animal easy and its egress
difficult or impossible.
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