STUDY OF A SPONGE. 315 



Crush a bit of the dry sponge between the fingers. How 

 does it compare with the other form ? Examine a very thin 

 bit of it under the microscope ; can you find spicules ? 



It is to be noted that in the bath-sponge only the hard 

 or skeletal parts are present, the flesh having been washed 

 away. In the calcareous sponge, as put up for laboratory 

 use, flesh and skeleton are both present. 



