ll'O 



THE HARMONIES OF NATURE. 



these compound polyps are at liberty to swim about in the sea, 

 as for instance the Pennatulae, or Sea Pens ; but few, like the 



Alcyonians, are of a spongy 

 or cork-like nature, cover- 

 ing submarine bodies with 

 shapeless masses. The 

 majority, like the Ked 

 Coral of the Mediterranean, 

 consist of a living and 

 soft rind, enveloping a 

 solid calcareous axis, or, 

 like the reef- building 

 Lithophytes of the tropical 

 seas, form populous colo- 

 nies inhabiting cells, dis- 

 tributed over the surface 

 of stony polyparies. 



The individual animals 

 of these social republics are 

 far inferior in size to the Sea-anemone, but their communities 



Peunatula Grisea. 



Alcyonidium 



(a) Branch to which the polypary is fixed ; (6) foot ; c trunk ; (d) polype bearing branches ; 

 (e) polyps contracted within the foot. 



frequently occupy a much larger space, so as to attain a diameter 

 or height of many feet. Like the plants which they frequently 



