72 CRINOIDEA 



ocean, and are rare ; the Feather Stars, on the other hand, are 

 comparatively common at depths of about 10 fathoms off the 

 south-west coast of England. 



In their mode of life the Crinoida differ entirely from all the 

 other Echinoderms, for instead of crawling about mouth downwards, 

 by the aid of tube-feet, they remain more or less permanently 

 fixed in one spot, and mouth upwards, either growing on a stalk, 

 or anchored by little clawed hooks to stones or seaweeds. The 

 Stalked Crinoids, or Sea-lilies, which are the living representatives 

 of the beautiful fossil Encrinites, or Stone-lilies, are very rare, but 

 their structure is fundamentally similar to that of the more abun- 

 dant and familiar Feather Stars. We will therefore take the Rosy 

 Feather Star (Antedon (Comatula) rosacea) as our type. The body 

 of this beautiful animal is star-shaped, with a central disk, and 

 five arms, which divide almost at their base into two, so that the 

 animal appears to be ten-armed. These arms are long and slen- 

 der, very flexible, and clad with short, slender branches or pinnules, 

 so that they look just like graceful feathers. Attached to the 

 middle of the back of the body-disk are a number of little, jointed, 

 clawed hooks, called the " cirri," by which the Feather Star 

 anchors itself to any rock or weed on the floor of the sea. On 

 the upper surface is the mouth, which may or may not be placed 

 centrally ; and the anus, the position of which is governed by 

 that of the mouth. The upper surface of each arm and pinnule 

 has a groove corresponding to the ambulacral groove on the arm 

 of the starfish, but lined with cilia instead of tube-feet ; and it 

 is by the constant movement of the cilia that currents are set 

 up in the water which carry tiny food particles along to the 

 mouth, where the grooves of all the arms converge. Occasion- 

 ally the Feather Star will swim about, probably changing its 

 quarters in search of food, or a more favourable position, and 

 then it moves through the water by very graceful undulations of 

 the long, slender, feathery arms. The young escape from the 

 egg as oval, free-swimming larvse a condition which lasts for a 

 day or two and then become fixed to a base by a slender stalk. 

 The arms are developed, and the little animal looks like a miniature 

 Sea-lily or Stalked Crinoid. Soon after the cirri, or anchoring 

 organs, appear the young Feather Star snaps off its stem and 

 swims away. 



