134 ZOOLOGY 



which they gain their food. They sometimes come to the 

 surface at night in search of companions and food (Fig. 

 122). Even during the day in rainy weather they extend 

 the anterior end of the body out of their burrows. Earth- 

 worms, found on the surface at other times, have, for the 

 most part, been parasitized by a fly, and are in consequence 

 weak or dying. During the daytime, if the surface mois- 

 ture permits, they lie near the mouth of their burrows, 

 probably for the sake of the sun's warmth. In this posi- 

 tion they can be seen by looking down into the holes. At 

 such times they are often caught by birds. In dry weather, 

 or when the ground is freezing, earthworms burrow deep 

 to a moist stratum, or to below the frost line, and hiber- 

 nate there. 



Food. Earthworms are omnivorous. As they burrow 

 through the ground, the earth is taken into the alimentary 

 tract, and the digestible particles are dissolved out and 

 absorbed as food. Earthworms can, however, be fed upon 

 green and dead leaves, decaying wood, seedlings, bits of 

 flesh, and even filter paper. Earthworms have the habit 

 of dragging into their burrows leaves which they intend 

 to devour. There the leaves are moistened with a fluid 

 excreted by the worm. This fluid partially digests the 

 food. After being taken into the alimentary tract, the 

 food reaches an organ of the canal known as the gizzard. 

 This part has thick muscular Avails, and contains in its 

 cavity small stones ; by the action of both the muscular 

 gizzard and the small stones, the food is ground up in 

 much the same way as are the grains of corn by the aid of 

 stones in the gizzard of a hen. 



Resistance and Regeneration. The capacity which earth- 

 worms possess of resisting certain untoward conditions is 



