_Food and Digestion_.—Worms are omnivorous. They swallow an enormous quantity of earth, out of which they extract any digestible matter which it may contain; but to this subject I must recur. They also consume a large number of half-decayed leaves of all kinds, excepting a few which have an unpleasant taste or are too tough for them; likewise petioles, peduncles, and decayed flowers. But they will also consume fresh leaves, as I have found by repeated trials. According to Morren {33} they will eat particles of sugar and liquorice; and the worms which I kept drew many bits of dry starch into their burrows, and a large bit had its angles well rounded by the fluid poured out of their mouths. But as they often drag particles of soft stone, such as of chalk, into their burrows, I feel some doubt whether the starch was used as food. Pieces of raw and roasted meat were fixed several times by long pins to the surface of the soil in my pots, and night after night the worms could be seen tugging at them, with the edges of the pieces engulfed in their mouths, so that much was consumed. Raw fat seems to be preferred even to raw meat or to any other substance which was given them, and much was consumed. They are cannibals, for the two halves of a dead worm placed in two of the pots were dragged into the burrows and gnawed; but as far as I could judge, they prefer fresh to putrid meat, and in so far I differ from Hoffmeister. Léon Fredericq states {34} that the digestive fluid of worms is of the same nature as the pancreatic secretion of the higher animals; and this conclusion agrees perfectly with the kinds of food which worms consume. Pancreatic juice emulsifies fat, and we have just seen how greedily worms devour fat; it dissolves fibrin, and worms eat raw meat; it converts starch into grape-sugar with wonderful rapidity, and we shall presently show that the digestive fluid of worms acts on starch. {35a} But they live chiefly on half-decayed leaves; and these would be useless to them unless they could digest the cellulose forming the cell-walls; for it is well known that all other nutritious substances are almost completely withdrawn from leaves, shortly before they fall off. It has, however, now been ascertained that some forms of cellulose, though very little or not at all attacked by the gastric secretion of the higher animals, are acted on by that from the pancreas. {35b}