20S ZOOLOGY. 



are no eyes, though these animals are sensitive to 

 the action of light. The earthworm is herma- 

 phrodite (p. 16); when two individuals pair they 

 mutually fertilize each other. On a warm summer 

 evening two adjacent worms creep half out or nearly 

 out of their burrows, and apply the front parts of 

 their bodies together, especially a reddish, swollen 

 part found at about the middle of the anterior half of 

 the body. In this region the glands in the skin are 

 very strongly developed, and secrete a substance 

 which surrounds the eggs as a capsule as they are 

 being laid. Earthworms are chiefly found in damp 

 humus, or, at any rate, not in very poor sandy soil 

 or clay. From time to time they carry their burrows 

 up to the surface in order to get rid of the undigested 

 remains (" worm castings ") of the humus and vege- 

 table matters which have been taken into the body. 

 The burrows run down obliquely into the soil, or more 

 rarely vertically, to the depth of eight feet or more ; 

 they end in an enlargement, where the worm remains 

 coiled up during the winter, after having closed the 

 mouth of the burrow with a plug of leaves, twigs, 

 paper, straw, etc. Although the earthworm chiefly 

 subsists on the organic matters found in earth rich in 

 humus, it also devours the leaves of cabbage, onion, 

 and other plants, and especially seedlings (particularly 

 those of beet). It draws these parts of plants about 

 four-fifths of an inch into its burrow, and moistens 

 them there with an acid fluid it secretes, and which 

 acts upon them before they are taken into the body. 

 Earthworms may efiect considerable damage by de- 

 stroying seedlings, particularly in damp fields, though 

 this damage is always local. A not inconsiderable 

 amount of benefit is to be set against this. By means 

 of the burrows which they dig earthworms cause air 

 to penetrate into the soil much better than it could 

 otherwise do, which is known to be of the greatest 

 importance for plant life. Earthworms are extremely 



