124 WESTERN SERIES OF READERS. 



other ways also. The mouths of both are in the 

 center, and the parts of the body reach out like 

 the spokes of a wheel. For this reason they are 

 sometimes called Radiates. 



But notice; how does the urchin differ from 

 the starfish? 



He has long thorns on his skin. 



Right. They are called spines, and very curi- 

 ous organs they are, too. They protect the 

 animal like a fence of bayonets, and they help 

 him in moving, also. What else? 



He has a hard shell. 



That is true; while the starfish has a leathery 

 skin with many stony points set in it. But find 

 an old sea-urchin shell that is broken, and notice 

 the many pieces of which the shell is made up. 

 And as the creature grows, each of these pieces 

 must be increased in size. What else? 



The sea-urchin seems to have a set of teeth. 



Good; and are they set in two jaws, like yours? 



No; there are only five teeth, and they all come 

 together in a point. Is n't it strange? 



Yes; it is very strange; and when you dissect 

 a sea-urchin you will be more and more surprised 

 to see what a wonderful mouth he has. For he 

 really has five jaws, with one tooth in each jaw, 

 and as the teeth wear off, they grow down from 



