Segmented worms with rounded (earthworm) or flattened (leech) bodies, and possessing both mouth and anus. They fall into two sub-classes: I. Leeches (_Discophora_), II. Bristle-worms (_Chætopoda_). The first possess suckers as organs assisting locomotion, the latter foot-stumps, which bear longer or shorter bristles; but these foot-stumps may be absent, and the bundles of bristles are then simply imbedded in pits. The latter is the case in the only members of the class which interest us here, _i.e._ the _earthworms_. The =Earthworms= (_Lumbricus_). There are several species in the genus, but all agree in their habits. The body of the earthworm is slender and cylindrical, tapering in front and somewhat flattened behind. On the ventral side of the second segment is found the opening of the mouth. There are no eyes, though these animals are sensitive to the action of light. The earthworm is hermaphrodite (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 vegetable 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 effect considerable damage by destroying 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 important owing to the large numbers in which they are present in the soil, and for another reason besides the one just given. Darwin shows that in many parts of England a