PHYLUM ECHINODERMATA 235 



by breaking loose at the constricted point where it joins the central 

 disc. This ability of self -mutilation is known as autotomy. Follow- 

 ing autotomy there is regeneration of a new part. 



Economic Relations 



Compared with many other animals the echinoderms are relatively 

 unimportant economically. The sea cucumbers of several different 

 species are used as food by the Chinese and other oriental people. 

 The larger animals, some of them two feet long, are eviscerated, 

 boiled, soaked in fresh water, dried or smoked and sold under the 

 name of heche-de-mer or trepang. This dried product is semileathery 

 and gelatinous. It is quite expensive and is usually served as a 

 very palatable soup. The chief fisheries are found along the shores 

 of China, the East Indies, Australia, and the Philippines; some, 

 however, are taken in California, Hawaii, and the "West Indies. 



Sea urchins of several kinds furnish a sort of caviar known as 

 "sea eggs." The egg masses are taken from the sexually mature 

 females and are eaten either raw or cooked. Each specimen con- 

 tains a considerable quantity of roe at the season just before 

 spawning. Production of "sea eggs" has become quite an industry 

 in the Orient, Italy, and the West Indies. The Barbados are par- 

 ticularly noted for their production of this commodity. 



Perhaps the starfish is the most important of the group, but its 

 relationship is almost entirely of negative importance. It is one 

 of the worst enemies of clams, oysters, and snails. The starfish 

 grows in enormous numbers around the oyster beds of the Atlantic, 

 attacks the oysters, and feeds on them, leaving only the empty 

 shells. A single starfish may eat as many as two dozen oysters in 

 a day. Oyster hunters formerly attempted to protect the oysters 

 and clams by dragging "tangles" made of frayed rope over the 

 beds, catching large numbers of starfish, breaking them in two, and 

 dumping the scraps back into the water. The fallacy of this was 

 realized when their power of regeneration was learned, so at present 

 they are usually dropped into boiling water or thrown on the bank 

 to dry. Salted or smoked starfish roe (eggs) are considered a 

 delicious food by many people. 



The brittle stars and crinoids have little value except as geologi- 

 cal indices and biological specimens. Their skeletal parts contribute 

 to the formation of limestone. 



