STAR-FISHES AND SEA-URCHINS. 6l 



shows you a portion of such a shell where the different 

 parts are still more clearly seen. The broader rays 

 with the largest spots are those along which the spines 

 were attached ; the narrower ones, with the smaller 

 spots crowded closely together, are those along which 

 the suckers were placed. 



There is a great variety among the Sea-Urchins, as 

 well as among the Star- Fishes. They do not all bur- 

 row in the rocks. Some of them are flat in form, and 

 live on sandy flats, burying themselves in the sand ; so 

 that they are only discovered when left bare after 

 storms, or in very still days, when, in changing their 

 place, they have left tracks along the sand. 



There is another animal, which, though it differs 

 strikingly in appearance from the Sea-Urchin and the 

 Star- Fish, is yet constructed on the same plan. It is 

 commonly called, 

 from its form, the 

 Sea- Cucumber.* 

 (No. 46.) It may 

 be a little difficult 

 to show you how 

 this soft elongated No - 46 - 



animal, resembling a worm more than any thing else, is 

 related to the Star- Fish with its extended rays, or to the 

 Sea-Urchin with its round outline ; but I will try to ex- 

 plain it to you. Imagine that the Sea-Urchin were elas- 

 tic, and that taking him at the mouth on one side, and 

 at the spot just opposite to the mouth where the rays 

 meet on the other side, you could stretch him out till, 

 instead of being a round, compressed ball, he would 



* Holothuria. 



