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Show 14 -IIABITS OF WORMS. CHAP. I. individuals, which are generally affected by the parasitic larvre of a fly, must also be excepted, as they wander about dnring the day and die on the surface. After heavy rain succeeding dry weather, an astonishing number of dead worms may sometimes be seen lying on the ground. Mr. Galton informs me that on one such occasion (March, 1881 ), the dead worms averaged one for every two and a half paces in length on a walk in Hyde Park, four paces in width. He counted no Jess than 45 dead worn1s in one place iu a length of sixteen paces. From the facts above given, it is not probable that these worms could have been drowned, and if they had been drowned they would have perished in their burrows. I believe that they were already sick, and that their deaths were merely hastened by the ground being flooded. It has often been said that uuder ordinary circumstances healthy worms never, or very rarely, completely leave their burrows at night; but this is an error, as White of Belborne long ago knew. In the morning, after there has been heavy rain, the film of n1ud or of very fine sand over graYcl-vvalks is often CHAP. I. W ANDEH FROM 'l'HEIR BURROWS. 15 plainly marked with their tracks. I have noticed this from August to May, both months included, and it probably occurs during the two remaining months of the year when they are wet. On these occasions, very few dead worms could anywhere be seen. On January 31, 1881, after a long-continued and unusually severe frost with much snow, as soon as a thaw set in, the walks were marked with innumerable tracks. On one occasion, five tracks were counted crossing a space of only an inch square. They could sometimes be traced either to or from the mouths of the burrows in the gravel-walks, for distances between 2 or 3 up to 15 yards. I have never seen two tracks leading to the same burrow; nor is it likely, from what we shall presently see of their sense-organs, that a worm could find its way back to its burrow after having once left it. They apparently leave their burrows on a voyage of discovery, and thus they find new sites to inhabit. Morren states* that worms often lie for hours almost motionless close beneath the mouths of their burrows. I have occasionally noticed the same fact with worms kept in • 'De Lnmbrici tcrrcstris,' &c., p. 14. |