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
Triangles of the above specified sizes were scattered on the ground in
many places and on many successive nights near worm-burrows, from which
the leaves, petioles, twigs, &c., with which they had been plugged, were
removed. Altogether 303 triangles were drawn by worms into their
burrows: 12 others were drawn in by both ends, but as it was impossible
to judge by which end they had been first seized, these are excluded. Of
the 303, 62 per cent. had been drawn in by the apex (using this term for
all drawn in by the apical part, one inch in length); 15 per cent. by the
middle; and 23 per cent. by the basal part. If they had been drawn
indifferently by any point, the proportion for the apical, middle and
basal parts would have been 33.3 per cent. for each; but, as we have just
seen, it might have been expected that a much larger proportion would
have been drawn in by the basal than by any other part. As the case
stands, nearly three times as many were drawn in by the apex as by the
base. If we consider the broad triangles by themselves, 59 per cent.
were drawn in by the apex, 25 per cent. by the middle, and 16 per cent.
by the base. Of the narrow triangles, 65 per cent. were drawn in by the
apex, 14 per cent, by the middle, and 21 per cent. by the base; so that
here those drawn in by the apex were more than 3 times as many as those
drawn in by the base. We may therefore conclude that the manner in which
the triangles are drawn into the burrows is not a matter of chance.
In eight cases, two triangles had been drawn into the same burrow, and in
seven of these cases, one had been drawn in by the apex and the other by
the base. This again indicates that the result is not determined by
chance. Worms appear sometimes to revolve in the act of drawing in the
triangles, for five out of the whole lot had been wound into an irregular
spire round the inside of the burrow. Worms kept in a warm room drew 63
triangles into their burrows; but, as in the case of the pine-leaves,
they worked in a rather careless manner, for only 44 per cent. were drawn
in by the apex, 22 per cent. by the middle, and 33 per cent. by the base.
In five cases, two triangles were drawn into the same burrow.
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