258 CCELENTERATES: POLYPS. 



this machine upon the coral beds, others row the boat 

 so that the branches broken off are caught up by the 

 nets. From time to time the cross and nets are raised, 

 and the branches of coral which have been entangled 

 in the meshes are secured. 



Closely related to the Gorgonias are the Alcyonacea, 

 of which the Organ-pipe Coral, Figure 495, is one of 

 the most interesting examples. It is of a beautiful 

 red color, and gets its name from the fact that the 

 tubes of the coral somewhat resemble organ-pipes. 



Sea Anemones, or Actinaria. 



These Polyps are wholly soft, only a few secreting 

 from the base a horn-like substance. The)' are com- 

 mon on nearly all coasts, and vary from a quarter of 

 an inch to a foot or more in diameter, as seen in some 

 of the tropical species. Our species seldom exceed two 

 or three inches in diameter, and most of them are much 

 smaller, although some are six inches high. The Bu- 

 nodes, Figure 499, is found among the rocks on the 

 coast of Maine. The most common kind on the north- 

 east coast of North America is the Fringed Actinia, or 

 Metridium. Figures 496-498. When fully expanded, 

 it is about four inches high and three inches across the 

 disk, and is a most interesting object. 



Madrepores, Porites, Meandrinas, Astrseans, etc., or 

 Madreporaria. 



These Polyps are simple or compound, often exces- 

 sively branching, and they form coral in their walls, or 

 outer parts, in their radiating partitions, and often at 

 their base. The forms which the communities assume 



