136 THE HARMONIES OF NATURE. 



ing of hundreds of nicely-fitted calcareous pieces arranged in a 

 regular pattern, perfectly symmetrical in all its parts ; so that 

 the supple animal finds no difficulty in making its way through 

 the crevices of a rocky shore, or in traversing the intricate tangles 

 in search of prey. The march of the sea-star is indeed but slow, 

 and hosts of little marine animals on which he would willingly 

 feed, no doubt escape his voracity, as they have been gifted with 

 a greater agility ; yet his table is richly furnished, for there are 

 hosts of molluscs that are not only more tardy than himself, but 

 even firmly rooted to the ground, and have nothing to oppose 

 to his attacks but the passive resistance of their closed valves. 



This defence, however, is frequently of no avail, for star-fishes 

 are not unfrequently found feeding, on shell-fish, enfolding their 

 prey within their arms, and seeming to suck it out of its shell 

 with their mouths, pouting out the lobes of the stomach, which 

 they are able to project in the manner of a proboscis. Possibly 

 the stomach secretes an acrid and poisonous fluid, which, by 

 paralysing the shell-fish, opens the way to its soft and fleshy 

 parts. Thus the star-fish is a sworn enemy to oyster banks, and 

 consequently also an indirect enemy to man ; but fortunately he 

 himself is an object of pursuit to greedy crabs, cephalopods, 

 and fishes, who, however, are frequently at some pains to catch 

 him ; for it is no easy matter to detach him from the rock 

 to which he clings, and the spines which frequently cover his 

 coriaceous back are likewise no despicable means of passive 

 defence. 



The sea-star might be called a flattened sea-urchin with 

 radiated lobe, and the sea-urchin a contracted or condensed sea- 

 star, so near is their relationship. Still there are notable dif- 

 ferences between them. Thus, in the sea-urchins, the digestive 

 organs form a tube with two openings, while in the sea-stars 

 they have but one single orifice. The mouth of the latter, 

 which may be so dilated as to admit large mollusca in their 

 entire shell, has only toothed processes projecting into its cavity, 

 but that of the sea-urchin is a masterpiece of mechanical con- 

 trivance. Fancy five triangular bones or jaws, each provided 

 with a long projecting moveable tooth. A complicated muscu- 

 lar system sets the whole machinery going, and enables the jaws 

 to play up and down, and across ; so that a more effective mill 

 for grinding down the food cannot well be conceived. 



