had he but brought coils to his aid,
might have simplified matters so easily. The little Heterodons, and
even the Lacertines, often assist themselves with coils in managing
their prey, though not themselves constrictors; but the venomous ones
have not the slightest notion of helping themselves in this way, as if
confident that in time their venom would do its work.

[Illustration]

WHAT WORMS DO

(FROM THE FORMATION OF VEGETABLE MOULD.)

BY CHARLES DARWIN.

[Illustration]

We now come to treat of a curious and important subject,--namely, the
amount of earth which is brought up by worms from beneath the surface,
and is afterwards spread out more or less completely by the rain and
wind. The amount can be judged of by two methods,--by the rate at
which objects left on the surface are buried, and more accurately by
weighing the quantity brought up within a given time. We will begin
with the first method, as it was first followed.

Near Maer Hall in Staffordshire, quick-lime had been spread, about the
year 1827, thickly over a field of good pasture-land, which had not
since been ploughed. Some square holes were dug in this field in the
beginning of October, 1837, and the sections showed a layer of turf,
formed by the matted roots of the grasses, 1/2 inch in thickness,
beneath which, at a depth of 21/2 inches (or 3 inches from the surface),
a layer of the lime in powder or in small lumps could be distinctly
seen running all round the vertical sides of the holes. The soil
beneath the layer of lime was either gravelly or of a coarse sandy
nature, and differed considerably in appearance from the overlying
dark-coloured fine mould. Coal-cinders had been spread over a part of
this same field either in the year 1833 or 1834; and when the above
holes were dug, that is, after an interval of 3 or 4 years, the
cinders formed a line of black spots round the holes, at a depth of
1 inch beneath the surface, parallel to and above the white layer of
lime. Over another part of this field cinders had been strewed, only
about half a year before, and these either still lay on the surface or
were entangled among the roots of the grasses; and I here saw the
commencement of the burying process, for worm-castings had been heaped
on several of the smaller fragments. After an interval of 43/4 years
this field was re-examined, and now the two layers of lime and cinders
were found almost everywhere at a greater depth than before by nea