Читать книгу Intelligence in Plants and Animals онлайн

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After swallowing earth, whether for making its burrow or for food, the earth-worm soon comes to the surface to empty its body. The rejected matter is thoroughly mixed with the intestinal secretions, and is thus rendered viscid. After becoming dried, it sets hard. When in a very liquid state the earth is thrown out in little spurts, and when not so liquid by a slow peristaltic movement of the intestine. It is not cast indifferently on any side, but first on one and then on another, the tail being used almost like a trowel. The little heap being formed the worm seemingly avoids, for the sake of safety, the use of its tail, the earthy matter being forced up through the previously deposited soft mass. The mouth of the same burrow is used for this purpose for a considerable time. When a worm comes to the surface to eject earth, the tail protrudes, but when it collects leaves its head must protrude, and thus worms must have the power of performing the difficult feat, as it seems to us, of turning round in their closely-fitting burrows. Worms do not always eject their castings upon the surface of the ground, for when burrowing in newly turned-up earth, or between the stems of banked-up plants, they deposit their castings in such places, and even hollows beneath large stems lying on the surface of the ground are filled up with their ejections. Old burrows collapse in time. The fine earth voided by worms, if spread out uniformly, would form in many places a layer of one-fifth of an inch in thickness. But this large amount is not deposited within the old unused burrows. If the burrows did not collapse, the whole ground would be first thickly riddled with holes to the depth of ten inches or more, which in fifty years would grow into a hollow, unsupported place ten inches deep.