6o 



STAR-FTSHES AND SEA-URCIUNS 



fringes on these animals should produce any effect on 

 a substance hard as granite ; yet we know that the con- 

 stant dropping of water wears away a stone, and it may 

 be that the continual friction even of the soft parts of 

 the Sea-Urchin would be equally effectual. 



The common Sea-Urchin of Nahant is one of those 

 that make these singular holes, and you may have an op- 

 portunity of seeing them in the rocks there. I hope you 

 will try to find some Sea-Urchins for your Aquarium next 

 summer, and watch them in their living condition. I 





No 44. 



No. 



45- 



dare say you have often seen them dead and dry on the 

 beaches, but you cannot then judge at all of their appear- 

 ance when living. They look very pretty when dried 

 in that way, because, though they have lost all their 

 spines and suckers, the spots where these appendages 

 were attached form a sort of pattern in regular rows or 

 zones over the surface of the animal, and you can 

 trace in this pattern the lines along which the spines and 

 suckers were arranged when the animal was living. No. 

 45 shows you such a dried Sea-Urchin shell; No. 44 



