PHYLUM ECHINODERMATA 



171 



sucker-like extremities and, like the tube-feet of the starfish, 

 are the organs of locomotion. A remarkable and charac- 



FlG. 94. 



- Strongylocentrotus. Entire animal, wi 

 the ends of the spines. (From Breh 



animal, with the tube-feet extended beyond 



— £.•. — 7-7 ... * 



tm's Tliierlcleti.) 



teristic feature of the internal structure is the presence of a 

 complicated apparatus for mastication known as Aristotle's 

 lantern, consisting of five jaw-like parts, each bearing a 



