"Oh, it is easy enough to move them. That can be done any time by means of a good tempting mulberry leaf; they will cling to it tight as a leach and you can cart them round wherever you wish." "When do you suppose our silkworms will first change their skins, Josef?" asked Pierre. "Moult?" "Yes. I forgot the word for it." "That all depends on the temperature of the room and on how fast they develop. Usually with the degree of heat we keep here the first moulting takes place within eight days. You see your silkworms are only about a quarter of an inch long at first, and as they increase in size to about three inches their skin is not elastic enough to accommodate their rapid growth. It simply won't hold them. Suppose you or Marie grew twelve times your natural size in a few short weeks?" "I'd pity Mother, letting out our clothes!" chuckled Marie. "They couldn't be let out; the material wouldn't be there," replied Josef. "And it would be the same way with your skin. It wouldn't stretch. You'd have to have a new one. That's what the silkworm does--only it does it several times over. No skin made can cover an animal that is a quarter of an inch long one week and three-quarters of an inch long the next, and so on growing in leaps and bounds until it gets up to three inches and sometimes more. Think of growing at that rate! And the little gourmands are not eating all the time, either, because after they are hatched it is three days before they eat much. They act stupid, and as if they didn't feel well. But later they make up for their loss of appetite--don't you fret." Josef smiled grimly. "By the fourth day they are eating at a furious rate," he went on, "and they keep right on stuffing themselves for five days. When they are about eight days old they have expanded until their skin is so tight that it makes them uncomfortable. It seems to pinch and make them ill. At any rate they act as if they felt pretty poorly and did not want to eat much more. Their next move is to cast their skins. This takes about three or four minutes and is a strenuous business while it lasts; every bit of the old skin goes--even that from the head, jaws, and feet. The ordeal leaves them weak and exhausted, but they soon cheer up, and are eating again furiously as ever. You can't stop them from eating very long." "How does the new skin look?" inquired Marie. "Just like the other?" "Why do you ask such foolish questions, Marie?" grumbled Josef. "Haven't you seen your father's silkworms hundreds of times?" "I'm ashamed to say I never noticed them very much, Josef," returned the girl. "They seemed such horrid little things that I never was interested in them."