EARTH-WORMS. 
61 
swell out, and thus push the earth away on all sides, while 
it also swallows the dirt, which passes through the digestive 
canal. In this way it may descend from three to eight 
feet in the soil. 
While earth-worms are in the main beneficial, from their 
habit of boring in the soil of gardens and ploughed lands, 
bringing the subsoil to the surface and allowing the air to 
get to the roots of plants, they occasionally injure young 
seedling cabbage, lettuce, beets, etc., drawing them during 
the night into their holes, or uprooting them.* 
Earth-worms lay their eggs in June and July, at night. 
Fig. 66.- Earth-worms, nat. size, a, embryo (blastula) soon after segmentation 
or tne yolk; 6, embryo further advanced; o, mouth; c, embryo still older; fc, 
primitive streak; d, neurula; o, its mouth. 
The eggs of the European Lumlricus rtiMhis are laid in 
dung, a single egg in a capsule; L. agricola lays numerous 
egg-capsules, each containing sometimes as many as fifty 
eggs, though only three or four live to develop. The de- 
velopment of the earth-worm is like that of the leech, the 
germ passing though a number of stages, the worm, when 
hatching, resembling the parent, except that the body is 
shorter and with a much less number of segments. 
The sea-worms have larger, more distinct bristles, as in 
Clymenella (Fig. 67), which lives in tubes in soft mud. 
*Darwin's Formation of vegetable mould through the action of worms. 
