C^CA OF STAR-FISH. 



129 



animal throagli a circular aperture, and being 

 furnished with a globular, membranous head, 

 just within the skin, filled with a fluid ; so that, 

 in fact, each foot or sucker bears some resem- 

 blance to a brass-headed nail driven through the 

 skin, the head remaining within the animal, and 

 the nail itself projecting. Now, if the creature 

 compresses the membranous head, the fluid con- 

 tained within it, being comparatively incompres- 

 sible, seeks an exit, and finds none except the 

 hollow of the tabe. Through this tube it accord- 

 ingly runs, and so pushes forward the sucker 

 which terminates the foot. When the pressure 

 is removed, the fluid returns into the head, and 

 the sucker is retracted. 



The mouth of the star-fish is placed under- 

 neath, and in the very centre of the body, the 

 stomach being immediately beyond the mouth, 

 as is the case with the sea-anemones. The 

 stomach does not seem to occupy very much 

 space, but it is capable of accommodating a large 

 amount of nutriment, in which it is assisted 

 by certain supplementary stomachs, which run 

 through each ray, nearly to its extremity. These 

 supplementary stomachs, or caeca, as they are 

 called, may be seen by slitting up the skin of 

 the upper surface of the rays, when the Cfcca will 



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