“The creature spins this cocoon to protect its chrysalis, of course. The silk is produced in two long, coiled tubes, which occupy nearly the whole length of the creature’s body. “Silk, before it issues from the caterpillar’s body, is a fluid. Whenever it comes out into the air, it becomes horny. Two strands are produced at once—one from each of the long coiled tubes. Before they leave the caterpillar’s body they are pressed together to form one flat, ribbon-like thread. Silk is one of the strongest fibres in the world. It is nearly as strong as steel, and much stronger than many of our metals. “In a fortnight your silken cocoons will produce white, fluffy moths. ‘Then you can supply your friends with hundreds of ‘silkworm’ eggs, and still have enough over to stock your larva cage.” [Illustration: Silk Moths—Male and Female.] Exercises on Lesson XIV. 1. Are “silkworms” really worms? What creatures do they most resemble? 2. Many of our common caterpillars spin silk of a kind. Take in “woolly bear” caterpillars. Feed them on the plants you find them on. Compare the cocoons they make with those of the “silkworm.” 3. Compare egg, larva, pupa, and perfect insect of the “silkworm” with that of the white cabbage butterfly. Does the caterpillar of the latter spin any silk? 4. Make a list of all the spinning insects you know, and try to explain the use of the “silk” thread in each case. APPENDIX. HINTS TO TEACHERS. STRUCTURE OF STEMS.—One- and two-year-old twigs of horse-chestnut, elm, and willow should be cut into half-inch lengths and distributed among the class. If cut straight across with a sharp pen-knife, the different layers can be seen with the naked eye. Afterwards these pieces should be slit longitudinally, and the various tissues _peeled off_ by the pupils. BULBS AND CORMS.—Bulbs of snowdrop and tulip, and corms of crocus, can be bought from seedsmen, from September to January, at from 6d. to 1s. per 100. At any other season of the year the onion will make a good substitute. WILLOW TWIGS will root readily if placed in water and kept near the hot pipes in school. VEGETABLE FINGERS.—To illustrate this lesson, peas (of any kind) ought to be grown in school. Branches of the many wild peas and vetches are to be found in abundance in every hedgerow during spring, summer, and autumn. Branches of Virginia creeper, clematis, tropæolum (Indian cress) may be shown with advantage. The compound leaves of the rose, ash, or mountain ash should be shown along with those of sweet-pea and edible pea, and the amount of green (assimilating) area compared. THE GREAT WATER BEETLE is found in nearly every pond. One or two should be kept and fed upon small worms. These beetles can also be obtained from any naturalist dealer. The larvæ of this beetle is found in ponds in summer months.