FeatJier Stars and Stone Lilies. 49 



place by means of numerous little tubular processes 

 which project through holes in the surface of the shell, 

 each of them ending in a little sucking disk. There are 

 five pairs of rows of these feet in most species, and 

 these, by attaching themselves and then contracting, 

 draw the body of the animal along. Each of these 

 pedicelli, or tube feet, as they are called, is hollow, 

 and contains water, and there are five long tubes in 

 each Echinoderm, which pass meridionally, and by fine 

 vessels convey the fluid m into the pedicelli from a 

 tubular ring which surrounds the mouth. To the 

 tubular system which supplies the little feet, the name 

 ambulacral system is given. This arrangement of 

 water-vessels connected with locomotion is peculiar 

 to Echinoderms. The sub-kingdom consists of four 

 chief classes. 



CLASS I. Encrinites (Crinoidea). These animals 

 abounded in former times in the seas of our globe, but 

 they are now for the most part extinct. The name is 

 derived from the resemblance of many of the fossil 

 forms to the flower of a lily, the infolded arms having 

 a petal-like appearance. With a few exceptions, they 

 are not, in their adult state, free and capable of loco- 

 motion, as are all other Echinoderms, but are fixed 

 on a jointed calcareous stalk. Though when first 

 hatched from the egg all Crinoids are free-swimming 

 ciliated bodies, yet very soon they settle down, develop 

 a stalk, and become rooted (fig. 28). There is a cen- 

 tral mouth, surrounded by a circle of movable arms, 

 which are often branched, and between these arms 

 are little plates pierced by holes through which the 

 ducts from the egg-producing organs open. In general 

 E 



