ECHINODERMATA. 275 



faculty of renewing organs which many of the zoophytes possess, we 

 will not here enlarge further upon the subject. 



The Crinoidae are not all like the two species which have heen 

 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 termi- 

 nates 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, com- 

 prehending 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. 



T 2 



