16 THE HALL OF SHELLS. 



have been strung of them, and such are found 

 in some of the most ancient sepulchers. 



"When you are well enough to go down 

 to the beach you will wonder at the power 

 of adhesion possessed by these little limpets, 

 for it is impossible to remove them from the 

 rocks without breaking their shells unless they 

 are surprised by sudden seizure. 



" Some authori'ties say this is owing to the 

 large round foot of the Patella, which is very 

 muscular and possessed of a viscous secretion 

 which aids it as a sucker. The perfectly even 

 edge of the shell keeps it tight against the 

 rock, while ' the power of treating a vacuum ' 

 — a problem too old for your young head — 

 is said also to enter into the operation. 

 Others attribute the adhesion to no muscular 

 action, but chiefly to the ' invisible glue which 

 exudes from the granulated base of the sole of 

 its foot,' as the expansion upon which the ani- 

 mal moves is called. We find upon removing 

 one of these little creatures from the rocks 

 that a sticky secretion is left where the limpet 

 clung. This gluelike substance is soon dis- 

 solved by the action of the sea water. 



" A weight of from twenty-eight to thirty 

 pounds has been suspended from the shell of a 

 limpet attached to a stone; the weight was 



