The Formation of Vegetable Mould Through the Action of Worms: With Observations on Their HabitsDarwin, Charles
Science
The Formation of Vegetable Mould Through the Action of Worms: With Observations on Their Habits
Darwin, Charles
Earthworms; Humification; Soils
The late Mr. John Scott of the Botanic Gardens near Calcutta made many
observations for me on worms living under the hot and humid climate of
Bengal. The castings abound almost everywhere, in jungles and in the
open ground, to a greater degree, as he thinks, than in England. After
the water has subsided from the flooded rice-fields, the whole surface
very soon becomes studded with castings—a fact which much surprised Mr.
Scott, as he did not know how long worms could survive beneath water.
They cause much trouble in the Botanic garden, “for some of the finest of
our lawns can be kept in anything like order only by being almost daily
rolled; if left undisturbed for a few days they become studded with large
castings.” These closely resemble those described as abounding near
Nice; and they are probably the work of a species of Perichæta. They
stand up like towers, with an open passage in the centre.
[Picture: Fig. 3: A tower-like casting. Fig. 4: A casting from the
Nilgiri Mountains]
A figure of one of these castings from a photograph is here given (Fig.
3). The largest received by me was 3½ inches in height and 1.35 inch in
diameter; another was only ¾ inch in diameter and 2¾ in height. In the
following year, Mr. Scott measured several of the largest; one was 6
inches in height and nearly 1½ in diameter: two others were 5 inches in
height and respectively 2 and rather more than 2½ inches in diameter.
The average weight of the 22 castings sent to me was 35 grammes (1¼ oz.);
and one of them weighed 44.8 grammes (or 2 oz.). All these castings were
thrown up either in one night or in two. Where the ground in Bengal is
dry, as under large trees, castings of a different kind are found in vast
numbers: these consist of little oval or conical bodies, from about the
1/20 to rather above 1/10 of an inch in length. They are obviously
voided by a distinct species of worms.
The period during which worms near Calcutta display such extraordinary
activity lasts for only a little over two months, namely, during the cool
season after the rains. At this time they are generally found within
about 10 inches beneath the surface. During the hot season they burrow
to a greater depth, and are then found coiled up and apparently
hybernating. Mr. Scott has never seen them at a greater depth than 2½
feet, but has heard of their having been found at 4 feet. Within the
forests, fresh castings may be found even during the hot season. The
worms in the Botanic garden, during the cool and dry season, draw many
leaves and little sticks into the mouths of their burrows, like our
English worms; but they rarely act in this manner during the rainy
season.
Public-domain text, read in full here on John Shaqi.
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