126 THE SEA SHOBE 



of carbonate of lime that form a dusty deposit within the galleries 

 are supposed to be the product of the rasping or drilling action of 

 these granules. 



The pin-shaped spicules of Cliona may be obtained for micro- 

 scopic examination by breaking any old oyster shell that has formed 

 its home, and brushing out the dust from the galleries ; or, a part 

 of the shell may be dissolved in acid, and the sediment examined 

 for spicules on a slip of glass. 



