This Flustra (Fig. 69) is very beautiful, forming a delicate little plantlike form about an inch and a half in size. But the crowning glory of these worms, as shown in the figure, is the circular crown of tentacles by which food is grasped as it passes by. Any one who has collected fossils in what is known as the Trenton limestone is familiar with the little fossil shell called Lingula, of which two thousand species are known. Curiously enough this little shell has come down to us to-day, and in Figure 70 we see the living Lingula of our waters with its long stem by which it fastens itself in the sand. Lingula resembles a small clam shell, has two perfect shells, and probably holds a place in many collections as a shell; yet Lingula is a worm which secretes a two-valved, unhinged shell, that is an almost perfect imitation of a bivalve mollusk. In the Santa Catalina Channel, California, from water six hundred feet in depth, I have dredged shells resembling those in Figure 71. They hung upon rocks in clusters, and were very striking in their rich colors of yellow, red, etc. In shape these Terebratulas, also common among the fossil shells, resemble ancient Roman lamps, and hence are called lamp shells. They too are worms, however, and many more shell makers called brachiopods. The "wick," a muscular stalk or byssus, becomes firmly attached to some object at the bottom. But in the instance of the little Lingula the stalk or anchor rope merely passes between the curious shells. If the latter are opened, we find a singular bridge or limy framework which is intended to support the soft parts of the bridge, a very conspicuous feature of which are what are called arms, long, ribbonlike, fringed processes (_a_) which are coiled up in the shell and serve as breathing organs and to obtain food as well. They can be extended some distance from the shells. The curious frame upon which they rest is well shown in Figure 72. It is on record that during the Sikh rebellion an entire English regiment was put to flight by a force of worms. The troops were marching through a forest when land leeches began to fall from every branch and leaf, dropping in such vast numbers that the men were almost crazed by the vicious bloodsuckers; hence they broke and ran for clear ground, where they could rid themselves of the terrible pests. Semper, the naturalist, states that he was driven from the forests of Luzon by these leeches, which fell upon him like dew. The ordinary leech of commerce (Fig. 73) belongs to this group. It has a sucking mouth, which bears three teeth. It was once much used by physicians for bleeding purposes, in fact, the animal derives its name from the fact that medical men in England were formerly called leeches. The leech had a high commercial value, over seven million being used in London in a single year, valued at ten dollars a thousand. Leech raising is a regular business in Russia, Bohemia, and Hungary.