ECHINODERMS 



3°9 



Mediterranean. Among those having unbranched arms is the pustule star 

 (Hemieuryale pustulata), which lives on corals, and clasps its arms round the 

 branches as shown in 

 the illustration. It is 

 remarkable for the fact 

 that its arms resemble 

 coral-branches in form 

 and colour, a similarity 

 which undoubtedly pro- 

 tects it from many 

 enemies, and is a strik- 

 ing instance of mimicry. 



The feather-stars 

 resemble the starfish 

 and brittle stars in 

 having arms, but differ 

 from them in being 

 permanently or tempo- 

 rarily attached to a 

 jointed stalk. Moseley's 

 sea -lily {Metacrinus 

 moseleyi) may be taken 

 as an example, and has 

 forty arms which are 

 all studded with small 

 feelers, instead of tiny 

 feet. The comatulids 

 differ from the other 

 feather-stars in discard- 

 ing their stalk after a 

 time and thenceforth 

 leading a free life. 

 One of the best known 

 species of this very 

 numerous family is the 

 rosy species of the Medi- 

 terranean and Atlantic 

 coasts of Europe {Ante- 

 don rosaceus), which 

 has a diameter of about 

 6 inches, and lives at 

 a depth of 30 fathoms, 

 where it is very com- 

 mon, clinging to coral-branches, worm-tubes, and the like. 



The sea-urchins (Echinoidea) have prickly bodies and no arms, and move by 

 means of their long tube-feet or their spines. Their size may have given rise to 



MOSELEY S SEA-LILY. 



