into the safety of the digestive cavity imbedded in 

 the main mass. In New England waters and north- 

 ward, species of the related Gersemia have salmon- 

 colored or reddish branches, or clusters of slender 

 lobes. Aiuhomastus, which looks like a red mush- 

 room with polyps strewn over the fleshy cap, is often 

 dredged up by fishermen on the New England coast, 

 and another species is known from deep waters oflf 

 California. Though some soft corals extend into po- 

 lar waters, this is largely a warm-water group with its 

 great center the Indo-Pacific Ocean. There, in shal- 

 low waters, the flabby masses of what look like leath- 

 ery seaweeds are alcyonacean colonies of moderate 

 size and of drab shades of yellow, brown, or olive. 

 Some run to dull reds or purples or other hues, and 

 in deeper waters they grow more treelike and are 

 stiffer( Plate 29). 



THE ORGAN-PIPE CORAL 



The organ-pipe coral, Tiibipora, is a spectacular 

 alcyonarian coral, with emerald-green polyps that 

 emerge from brick-red limestone tubes. In some trop- 

 ical waters it is an important reef-builder, though the 

 massive layers of tubes, laid down over many gener- 

 ations, are not secreted as solid limestone as in true 

 reef corals, but consist of fused spicules and lie within 

 the living tissue of the coral. Tiibipora belongs to 

 the stoloniferans, a group with some small members 

 in temperate waters that are the most primitive of 

 alcyonarians. In these the polyps are not fused to- 

 gether but arise separately from a basal mat of run- 

 ners. In the organ-pipe coral, however, the vertical 

 limestone tubes that house the polyps are joined at 

 intervals by horizontal platforms in which run con- 

 necting digestive canals. As the colony grows, the 

 lower levels of the tubes are abandoned, and they be- 

 come great tenements housing worms, small crabs, 

 and innumerable other little animals (Plate 54). 



THE BLUE CORAL 



The blue coral, Heliopora, which does not look 

 blue when the brown polyps are fully extended, is 

 found on the coral reefs of the Indo-Pacific. The blue 

 color of the broadly lobed calcareous skeleton is said 

 to be due to iron salts, and the limestone mass is 

 composed not of fused spicules as in other alcyonar- 

 ian corals, but of fibers of crystalline calcium carbon- 

 ate (aragonite) fused into sheets. The polyps live 

 only in the surface portions of the cylindrical cavities. 



THE GORGONIANS 



The gorgonians or horny corals include the sea 

 whips, sea fans, and sea plumes, which have a flexi- 

 ble skeletal core of a horny material called gorgonin. 

 Of plantlike growth form, and colored vivid shades 

 of yellow, red, orange, and purple, they furnish most 

 of the "blossoming shrubbery" of Atlantic shores, 



In the sliallow waters of Iiulo-Pacific reefs the soft 

 corals are mostly great flabby masses of what look 

 like leathery brown seaweeds. (Great Barrier Reef. 

 Fritz Goro: Life Magazine) 



adding much to the invertebrate lure that brings so 

 many skin divers to the shallow waters of Mediterra- 

 nean, Caribbean, and Florida coasts. They are really 

 most abundant in the tropical Indo-Pacific, but there 

 they are inconspicuous in shore waters compared 

 with the soft corals or the true reef corals. 



Though mostly coastal or from waters no more 

 than three thousand feet deep, gorgonians occur at 

 all depths. Many are luminescent, and when the 

 Challenger expedition in the 1 870's was discovering 

 so much that was new that everything since has been 

 anticlimax, all the alcyonarians dredged from deep 

 waters were seen to be brightly luminescent as they 

 came on board, one shrublike gorgonian glowing 

 with a soft pale lilac light. The larger deep-water col- 

 onies may reach 9 feet; and in the deep waters of 

 Norwegian fjords the bright scarlet Paragorgia at- 

 tains treelike growths. The shallow-water Lopho- 

 gorgia chilensis is seen by aqualung divers on the 

 rims of underwater canyons off La JoUa, California, 

 as sparsely scattered, low-branching, coral-colored 

 shrubs with white polyp "blossoms." Common in the 

 same places is the reddish purple Eiigorgia rubens. 

 Typically, gorgonians have slender whiplike branches 

 arising from a short main trunk that is firmly fastened 

 to the bottom. When the stems have side branches 



[101 



A deep-water soft coral, showing the lovely treelike form typical of alcyona- 

 ceans from the deeper waters of the Indo-Pacific region. ( Aquarium of Nou- 

 mea, New Caledonia. Rene Catala) 



