STARFISH AND OTHER ECHINODERMS 371 



at the constricted point wkere it joins the central disc. This ability 

 of self-mutilation is known as autotomy. Following 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, how- 

 ever, 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 particularly 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 futility 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 de- 

 licious food by many people. 



The brittle stars and crinoids have little value except as geological 

 indices and biological specimens. Their skeletal parts contribute to 

 the formation of limestone. 



