354 EVENINGS AT THE MICROSCOPE. 



The fleshy substance which surrounds these canals is 

 of a loose, spongy character, and grates beneath the 

 knife : a circumstance which is owing to the predomi- 

 nance of the calcareous element here, as you will see 

 when I extract a small portion of it, and, laying it on a 

 slip of glass, treat it with caustic potass. The micro- 

 scope now reveals a large number of spicula, far larger 

 than those we have hitherto observed, and different 

 from either sort in form. These resemble very gnarled 

 branches of oak, with the branchlets broken off close to 

 their origin, leaving ra<™ed and starred ends. 



