Because it swallows the soil or earth, from which, in its passage through the intestines, it extracts its nourishment.* Mr. Leon Dufour has recently determined the earth-worm to be an oviparous and not a viviparous animal. The eggs resemble a chrysalis or a cocoon, but their pulp, etc. prove them to be true eggs.
* In a recent paper in the Foreign Quarterly Review we read of other earth-eaters, in South America, where the women, children, serpents, lizards, and ounces of the river St. Francisco have a singular and most economical propensity of eating earth. It seems that the soil contains a small portion of salt-petre, which is agreeable to the palate. Boys and girls, however, are less select in their tastes, and sometimes eat the whitewash off the walls, and occasionally, wood, charcoal, or cloth.
The lower we go in the scale of creation, the more surprising is the reproductive faculty. The gardener cuts the earth-worm with his spade; but the injury, far from diminishing animal life, increases it; for each portion of the animal so divided, becomes a separate creature, having a system of parts speedily regenerated.