The Crinoïdæ are not all like the two species which have been described. There is an entire family of animals belonging to this class, namely, the _Comatula_, which are fixed in their early days, but separate themselves from the rooted stem in their adult age, and, throwing off the bonds imposed on their youth, live side by side with the asterias, with whose company they seem much pleased. The encrinites and the star-fishes thus live in company, and that at prodigious depths, and under a body of water which no light can reach. Imagine the existence of animals which pass their lives in such eternal funereal darkness. The family of Comatula are found in the seas of both hemispheres. Their bodies are flat--a large calcareous plate formed like a cuirass upon their backs--presenting, besides, cirri composed of numerous curling articulations, the last of which terminates in a hook. The ventral surface presents two orifices: the one in the centre corresponding to a mouth, the other evidently intended for the discharge of the products of digestion. This animal is provided with five arms, which diverge directly from the centre plate or cuirass. The branches of these arms have _ambulacral grooves_, comprehending a double row of fleshy tentacles, in the centre of which is the ambulacral groove, properly so called, clothed with vibratile cilia over their whole surface. These cilia or hairs guide the current which drives the various substances on which it feeds, such as the organic corpuscles of sea-weeds, and microscopic animalcules floating in the sea, towards its mouth. They are also powerful aids to respiration. The movements of these curious creatures are very slow, their only object being to catch the bodies of animals and marine plants, or, by extending or contracting their arms, to feel their way through the water to some new locality. Sometimes, also, in order to change their feeding-ground, the Comatula abandon the submarine forests, herbage, and sea-wracks, and float through the water, moving their arms with considerable rapidity in search of a new station. The Mediterranean Comatula (Fig. 109) is largely diffused on the European shores of the Mediterranean. Its spreading arms extend to three or four inches; its colour purple, shaded, and spotted with white upon the ventral surface. [Illustration: Fig. 109. Comatula Mediterranea (Lamarck), natural size.]