304 COMMON OBJECTS OF THE SHORE. 



exact are they, that a good zoologist can determine 

 the species by the examination of a single spine ; a 

 circumstance most important when investigating 

 their remains in a fossil state, as sometimes this 

 may be the only portion which he can procure. 

 Most wondrously suited to the wants of the living 

 creature within the cell, is the structure of these 

 spines. No rock is so smooth or so rugged but 

 that by their help the animal can make its way. Its 

 meal lies before it among the rocks ; the zoophytes, 

 the shell-fish, the crabs, are all welcome prey, nor 

 are they longed for in vain. To look at it, it 

 would seem a mere ball, incapable one would 

 imagine of attacking or seizing any living thing 

 that had limbs with which to walk away, or fins 

 by means of which it could glide out of its 

 presence. One would deem it almost like the 

 zoophyte, chained to its native rock. Not so ; it 

 can climb to places where animals which seem 

 better fitted for locomotion would find access im- 

 possible. Cased in a coat of mail, and furnished 

 with hundreds of spines which serve as legs, the 

 ball moves gently onwards. If an approaching 

 enemy gives notice of danger, it can either with- 

 draw behind some nook, or with the spines dig a 

 hole in the sand, and lie there till it is past. 

 Besides the spines, countless suckers aid the pro- 

 gress ; suckers, which like those on the star-fish, 

 emerge from the calcareous case, and which are as 

 long as the spines themselves. These suckers are 

 like little feet, and adhere firmly to rocks, and 

 serve too as means of offence and defence to the 

 animal ; for if the crab or fish is touched by them, 

 the touch proves fatal, and the victim is at once 

 dragged to the mouth and devoured. Its mouth 



