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Three species of pine-leaves are mentioned by Darwin as being regularly drawn into the mouths of worm-burrows on the gravel-walk in his garden. These leaves consist of two needles, which are united to a common base, and it is by this point that they are almost invariably drawn into the burrows. As the sharply-pointed needles diverge somewhat, and as several are drawn into the same burrow, each tuft forms a perfect chevaux-de-frise. Many tufts were pulled up in the evening, but by the ensuing morning fresh leaves had taken their places, and the burrows again well protected. Impossible it would be to drag these leaves to any depth into the burrows, except by their bases, as a worm cannot seize hold of the two leaves at the same time, and if one alone were seized by the apex, the other would be pressed against the ground and resist the entry of the one that was seized. That the worms should do their work well, it was very essential that they drag the pine-leaves into their burrows by their bases, that is, where the two needles are conjoined. But how they are guided in this work was at first perplexing. The difficulty, however, was soon settled. With the assistance of his son Francis, the elder Darwin set to work to observe worms in confinement during several nights by the aid of a dim light, while they dragged the leaves of the aforementioned kinds into their burrows. They were seen to move the anterior extremities of their bodies about the leaves, and on several occasions when they touched the sharp end of the needle they suddenly withdrew as though they had been pricked, but it is doubtful that they were hurt, for they are indifferent to sharp objects, being known to swallow rose-thorns and small splinters of glass. It may be doubted whether the sharp end of the needle serves to tell them that is the wrong end to seize, for the points of many were cut off for the length of an inch, and these leaves were always drawn in by their bases and not by the cut-off ends. The worms, it seemed, almost instantly perceived as soon as they had seized a leaf in the proper manner. Many leaves were cemented together at the top, or tied together by fine thread, and these in the majority of instances were dragged in by their bases, which leads to the conclusion that there must be something attractive to worms in the base of pine-leaves, notwithstanding that few ordinary leaves are drawn in by their base or footstalk. Leaves of other plants, and also the petioles of some compound plants, as well as triangular bits of paper, dry and damp, were experimented with, and the manner of seizing the objects and bearing them into their burrows were as amusing as they were novel and interesting. The leaves and stems used were such as the worms had not been accustomed to in their respective haunts.