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Show 108 TIABITS OF WORMS. CIIAP. II. which were measured was 3·B inch in height and 1 in diameter. .A. small cylindrical passage runs up the centre of each tower, through which the worm ascends to eject the earth which it has swallowed, and thus to add to its height. .A. .structure of this kind would not allow leaves being easily dragged from the surrounding ground into the burrows ; and Dr. King, who looked carefully, never saw even a fragment of a leaf thus drawn in. Nor could any trace be discovered of the worms having crawled down the exterior surfaces of the towers in search of leaves; and had they done so, tracks would almost certainly have been left on the upper part whilst it remained soft. It does not, however, follow that these worms do not draw leaves into their burrows during some other season of the year, at which time they would not build up their towers. From the several foregoing cases, it can hardly be doubted that worms swallow earth, not only for the sake of making their burrows, but for obtaining food. Hensen, however, concludes from his analyses of mould that worms probably could not live on CuAP. II. DEPTH OF THEIR BURROWS. 109 ordinary vegetable mould, though he admits that they might be nourished to some extent by leaf-mould.* But we have seen that worms eagerly devour raw meat, fat, and dead worms ; and ordinary mould can hardly fail to contain many ova, larvm, and small living or dead creatures, spores of cryptogamic plants, and micrococci, such as those which give rise to saltpetre. These various organisms, together with some cellulose from any leaves and roots not utterly decayed, might well account for such large quantities of mould boing swallowed by worms. It may be worth while here to I'ccall the fact that certain species ofUtricularia, which grow in damp places in the tropics, possess bladders beautifully constructed for catching minute subterranean animals; and these traps would not have been developed unless many small animals inhabited such soil. The deptlt to wlticlt worms penetrate, and the construction of tlzeir burrows. - Although worms usually live near the surface, yet they burrow to a considerable depth during long- * ' Zeitschrift fiir wisscnschaft. Zoolog.' n. xxviii. 1877, p. 364. |
