In order to obtain the materials for her brickmaking the Melicerta must have the power of modifying the direction of the ciliary currents, so as to throw a stream of small particles into the mould, which is a muscular organ, and capable of secreting a waterproof cement, by which they are fastened together. The result is, not to produce anything like the tubes made by the caddis-worms out of grains of sand, but entirely to change the appearance of the materials employed. All large particles are rejected, and only those retained which will form a homogeneous pulp with the viscid secretion; and when the process is complete the head of the creature is bent down, and the pellet deposited in its appropriate place. Each pellet appears originally to possess a more or less conical figure, but when they are squeezed together to make a compact wall they all tend to a hexagonal form, by which they are able to touch at all points, and any holes or interstices are avoided. According to Professor Williamson the young Melicerta commences her house by secreting "a thin hyaline cylinder," and the first row of pellets are deposited, not at the base as would be expected, but in a ring about the middle of the tube. "At first new additions are made to both extremities of the enlarging ring; but the jerking constrictions of the animal at length force the caudal end of the cylinder down upon the leaf, to which it becomes securely cemented by the same viscous secretion as causes the little spheres to cohere." Round the margins of the lobes or expansions may be seen delicate threads towards which others radiate; these are thought by Mr. Gosse to be portions of a nervous system, and two calcars or feelers serve as organs of relation. The young Melicertas are likewise furnished with a pair of eyes, which are probably rudimentary, and disappear as they grow up. The Melicerta tubes, being large enough to be visible to the naked eye, are easily crushed in the live-box, and to avoid this, they are conveniently viewed in a shallow glass cell, covered up as before described. By occasionally changing the water one may be kept for days in the same cell, and will reward the pains by frequently exposing its flower-like head. Usually the horns or feelers come out first, and then a lump of flesh. After this, if all seems right, the wheels appear, and make a fine whirlpool, as may be readily seen by the use of a little indigo or carmine.