SEA-STARS AND SEA-URCHINS. 89 



madrepore coral. I have already referred to the hydraulic 

 system by which the sucker-feet are distended and worked, and 

 this is the "intake" of the supply, as a water-company would 

 call it. Within these is a tube, running near to the creature's 

 mouth on its lower surface, and connecting with a ring of tube 

 that surrounds the mouth, and sends out a branch to each of 

 the five rays. To this branch-pipe all the sucker-feet in a 

 particular ray are connected, and the pressure can be so 

 regulated as to alternately distend the sucker-feet, or to 

 leave them partly empty and flaccid. 



Upon one occasion, when I was describing these arrange- 

 ments of the Stars to a jocular friend, he said the idea of 

 having a big mouth that let in water freely, and a number of 

 minute mouths that let it in slowly, reminded him of the poet 

 Cowper's whim in making a large aperture for his big hares 

 to pass through, and a small one for the little hares. He 

 thought the mouth would have served both purposes ; but as I 

 pointed out to him, the water that the Star takes in involunta- 

 rily with its food goes into the stomach, where the food is 

 retained and the water strained off by the mouth again. This 

 water would contain grains of sand, vegetable debris, and 

 other impurities, which would clog the delicate tubes and 

 spoil a beautiful piece of mechanism. The water that perco- 

 lates through the minute pores of the stony plate must be 

 pure, and free from all extraneous matter, so that the special 

 supply-pipe is a necessity. The scientific appellation of the 

 sucker-feet is pedicels or ambulacral feet. 



We must not omit to mention organs of another sort that 

 occur in plenty among the sucker-feet, and for many years 

 presented a puzzle to naturalists, who long regarded them as 

 parasites something foreign to the Star-fish. They are now 

 understood to be pedicels that have been specialised to adapt 

 them for particular functions. They consist of slender flexible 

 stalks, ending in an enlarged head of three claws which nor- 

 mally converge to a point, but they are for ever opening and 



