The first thing you see is a dark, brick-colored, cylinder-shaped house which looks to be about the size of a cigar. The little builder who lives in this house has been disturbed by the means we have taken to make his acquaintance; he has stopped work and gone within. But he is so industrious a fellow that he will not remain within very long. As soon as it is quite still he will probably come to the door of his house, and you will see him thrust out two horns. He will move these horns to the right and left, cautiously feeling all around him. He seems very cautious indeed. But at last he is satisfied that no enemy is near. Now he ventures out. He unfolds his wheels. These wheels are surrounded with a band of _cilia_, or flexible hairs, which he can put in rapid motion, making the wheels have the appearance of revolving very fast. This rapid motion of the cilia forms a swift current in the water; and this current brings tiny particles of various things to the little mechanic. Some of these particles he uses for food; of others, he makes brick. They are carried into an opening between the wheels where you can see them revolving very fast until they are gathered into a little round, dark-colored pellet. The particles are probably held together by a sticky secretion made by the builder. It takes him about three minutes to make a brick. As soon as it is finished, he bends his head over, takes it from its mould between the wheels, and lays it down carefully by the side of the last. Then he raises his head and begins to make another. The tube thus constructed is quite firm and strong. Sometimes when I have found a long tube, I have cut off a portion from the top. This can be done, with care, for the brickmaker drops to the bottom when disturbed. It is very amusing to watch him repair damages and rebuild. Sometimes I have forced one out of his tube, but it always soon died. But though industrious, he is so cautious, or timid, that he is easily frightened, and therefore he is often interrupted in his work. For instance, like some people that we know, he is very afraid of snakes. If a harmless little tiny snake comes wriggling along through the water anywhere near him, he folds his wheels and drops down into his house as quick as a flash. One day a little boy was delighted with the fast-revolving wheels. Suddenly, by and by, he turned toward me with great disgust plainly showing in his face: "He's gone in, 'fraid of a little snake!" he exclaimed. [Illustration: FIGURE 1, BRICKMAKER; 2, CURRENT IN WATER; 3, 4, 5, 6, DIATOMS; 7, 8, DESMIDS; 9, ALGAE; 10, 11, TRICHODA LYNCEUS; 12, SNAKE-LIKE LARVA; 13, PART OF PLANT TO WHICH BRICKMAKER IS ATTACHED; 14, BATRACHOSPERMUM MONILIFORM.]