62 STARFISHES 



the Starfish are a number of very remarkable bodies, microscopic 

 in size, which, when examined with a strong magnifying glass, 

 are seen to have the form of minute pincers, each consisting of 

 two movable blades crossing each other below and articulated to 

 a basal piece. The function of these curious organs, which are 

 called pedicdlarice, is to keep the Starfish clean by seizing 

 hold of any particles or small organisms which might attempt to 

 settle on the skin. When touched, these tiny blades open and 

 then snap together smartly. 



On the upper surface of the body, and situated in a space 

 between two of the rays, may be seen a small, round plate, the 

 surface of which is covered with fine grooves. This is the madre- 

 porite, through which water is constantly being drawn by the 

 action of cilia into the water-vascular system. Near the centre 

 of the upper surface may also be made out the minute opening 

 of the anus, for the discharge of effete matters. 



The mouth of the Starfish opens through a short passage (the 

 oesophagus) into a wide, five-lobed sac or stomach, the walls 

 of which are greatly folded ; each of the lobes is opposite one of 

 the rays, and the whole sac is capable of being everted through 

 the mouth, folded over any object desired as food, and then by 

 means of special retractor muscles withdrawn once more into the 

 interior of the body. Dorsally, this remarkable sac-like stomach 

 communicates with a small chamber, which in turn opens into a 

 very short, conical intestine leading directly upwards to open at 

 the surface by the anus. 



The Starfish is one of the great pests of the oyster fishery, and 

 is responsible for a very great financial loss annually, owing to 

 its depredations on the oyster beds, for it is very partial to a 

 meal of the best native oysters. According to Schiemenze, 1 who 

 has carried out a number of experiments, a bivalve may be cap- 

 able of resisting a sudden pull upon its shells of 4,000 grammes, 

 but sooner or later has to yield to a steady, prolonged pull of 900 

 grammes, while a Starfish can exert a steady pull of some 1,350 

 grammes. Now, the Starfish seizes the oyster, and folding itself 

 umbrella fashion over its prey, so that the edges of the valves of 

 the oyster are brought near the mouth, the tube-feet of the middle 



1 Mitth. des deutschen Seefischerve reins , xii., 1896, and Journal Marine Biological 

 Association, iv., 1895-97, p. 366. 





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