CHAPTER XI 



The Phoronids 



(yPJiylii ut Pit 01 oit idd) 



B, 



'ELOW the level of low tide, pier pilings in the 

 Bay of Naples wear a feltwork of interlacing mem- 

 branous tubes two or three inches thick. Each tube 

 is the individual home of a wormlike animal, Pho- 

 ronis kowalevskii. Like the fourteen other species 

 comprising this phylum, these tube-dwellers wear 

 a horseshoe-shaped crown of ciliated tentacles with 

 which they entrap food particles in a mucous film 

 carried to the mouth at the bottom of the horseshoe. 

 Most phoronids are less than 8 inches long, some 

 as short as Vid of an inch. A giant is Phoronopsis 

 califoniica. which lives singly in the estuaries along 

 the California coast in blind tubes as much as 18 

 inches long and -y, ,; of an inch in diameter. The en- 

 tire 1 2-inch body of this phoronid is orange, its tenta- 

 cles an even brighter shade of the same color. Some- 



times it leaves the %-inch plume of orange tentacles 

 exposed at the end of its sand-impregnated tube, and 

 draws attention in this way. 



On the Atlantic coast of North America, 5-inch 

 P/iorouis architecia is common in the sand flats of 

 North Carolina and as far north as Chesapeake Bay. 

 It also builds isolated tubes. 



In Australia, a diflerent reddish-colored phoronid 

 as much as 6 inches long builds a home for itself in 

 the wall of another tubedweller, the tube anemone 

 Ceriantlms. 



Phoronids have red blood in a closed system of 

 vessels. Most are hermaphroditic, and the fertilized 

 eggs develop into swimming larvae. Eventually the 

 young settle down to build a tube and grow by meta- 

 morphosis into adult form. 



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