126 



STRUCTUKE OF ECHINODERMATA. 



of a great number of pieces, very regularly arranged and 

 united together (fig. 69, e ) ; but these pieces are for the most 



Fig. 67. HOLOTHURIA. 



part only repetitions of one another ; and the different 

 portions have not that variety of uses which we see in higher 

 animals. With the exception of 

 the tribe of Encrinites or lily-like 

 animals (fig. 68), of which there are 

 very few now existing, but which 

 were very abundant in former ages, 

 all the animals belonging to this 

 class are unattached, and are capa- 

 ble of moving freely from place to 

 place. Their motions are very 

 sluggish, however, and are princi- 

 pally effected by means of an im- 

 mense number of minute tubular feet 

 (fig. 68, c), furnished with suckers 

 at their extremities, which can be 

 projected from almost any part of 

 the body. These are seen in rows 

 on the under side of each arm of 

 the Star-fish; they are put forth 

 through rows of very minute aper- 

 tures in the shell of the Sea- 

 Urchin (commonly termed the Sea- 



Fig. 68. ENCRINITE. 



