OF THE SPONGIAD^E. 227 



with a half-inch or two-thirds combination, and again with 

 not less than a quarter-inch object-glass, and the characters 

 of the various tissues in their natural condition be immedi- 

 ately noted. But the whole of their minute organs will not 

 be visible by this mode of examination, and it is therefore 

 necessary to mount the same or similar sections in Canada 

 balsam, by which means the spicula of the sarcode and other 

 minute organs will become completely visible in situ, and 

 the specimens thus mounted will serve as permanent records 

 for the cabinet. 



