202 METAZOAN PHYLA 



231. Regeneration and Autotomy. — The starfish has a considerable 

 power of regeneration. If the disc is deprived of all its rays it will 

 regenerate them all, and a single ray with only a portion of the disc will 

 regenerate the whole animal (Fig. 115). 



The starfish also possesses the power of autotomy. Ordinarily the 

 part dropped off is regenerated. This abiUty serves as a safeguard to 

 the animal which, if it finds itself caught by one or more rays, can simply 

 drop them off and make its escape. 



232. Economic Importance. — Starfishes are of economic importance 

 only as they are enemies of oyster fishermen or as they destroy clams and 

 other marine animals which serve as human food. Oysters live adherent 

 to solid objects lying upon the bottom of the sea in areas known as 

 oyster beds. Starfishes come upon these oyster beds and destroy 

 the oysters in the manner already described (Sec. 228). Ownere of oyster 

 beds fonnerly were in the habit of using drags made of ftayed rope ends 

 which they hauled over the beds behind a vessel and in which the star- 

 fishes became entangled. The drag with its starfishes was then hauled 

 upon the deck. The starfishes were chopped to pieces and thrown back 

 into the water, but since the pieces were capable of regeneration this 

 simply multiplied the number of animals. It is now the practice to 

 carry them to shore and deposit them above high water mark where they 

 are left to die. They may then be used as a fertilizer. The amount of 

 damage done by starfishes may be considerable if they are not actively 

 combated. A single one placed in a dish containing some clams of good 

 size was observed to devour over 50 of these in six days. 



