LOWER ANIMALS 



203 



each side of the skeleton, but no polyp reaches 

 the colony base; often called sea fans, sea feathers, or 

 sea whips according to extent of colony branching; 

 found mostly in tropical and subtropical waters, but 

 one type occurs at Newport Bay, California. 



ORDER PENNATULACEA (Sea Pens) 



Diagnosis: colony feather-like, fleshy, with leaf- 

 like polyps borne on each side of a very long, stem- 

 like polyp, the stalk; stalk usually embedded in sand 

 or mud; skeleton of separate spines, occur on soft 

 bottoms, mostly in warm waters; frequently found 

 in shallow water in bays where they can sometimes be 

 seen from a boat; some deep-water species have truly 

 remarkable powers of expansion and contraction, the 

 extremes showing a change on the order of three 

 times the body length; includes the bay-inhabiting 

 sea pansy (Renilla) of warm Pacific waters up to 

 southern California, a purple animal in which the 

 polyps grow from a single leaf-like structure above 

 the stalk. 



Subclass ZOANTHARIA 



Diagnosis: tentacles of various numbers, but never 

 eight; solitary or colonial; with or without a skeleton. 



ORDER ACTINARIA (Sea Anemones) 



Diagnosis: solitary but some closely grouped; no 

 skeleton; polyp columnar, base usually attached to 

 substrate by a suction disc, but not fixed to substrate; 

 those lacking a suction disc have a pointed, rounded 

 or bulb-like base. 



The sea anemones are perhaps the best known of 

 our intertidal coelenterates. Many people have sat 

 on a tidepool rock to discover to their sorrow that 

 what seemed to be solid rock was covered by very wet 

 anemones. Many will remember having either poked 

 them to watch the slow contraction of the body or 

 dropped a rock on the mouth of an anemone to watch 

 the rock being taken in and, later, rejected as food. 

 These animals are very interesting from many re- 

 spects. For example, their digestive juices are among 

 the most effective in the animal kingdom. Also, 

 some are the easiest tidepool animals to keep alive 

 in captivity. One kind of anemone was kept alive in 

 a quart jar for over thirty years. The remarkable 



thing about this situation is that the water was rarely 

 changed more often than once a week. 



ORDER MADREPORARIA {Sfony Corals) 



Diagnosis: mostly colonial; skeleton present; 

 polyps small in cups of coral skeleton; mostly in 

 warm, shallow waters; main contributors to coral 



reefs. 



These true corals are well known for their reef- 

 building habits. Stony corals are found in warm, 

 shallow waters of the world. Many United States 

 species occur, but the only semblance of coral reefs 

 are formed off Florida coasts. Both solitary and 

 colonial species are known along the Pacific Coast, 

 but even the colonial species have fairly distinct, 

 more or less isolated individuals with no real tend- 

 ency toward reef-building. 



ORDER ZOANTHIDEA {False Sea Anemones) 



Diagnosis: mostly colonial, with polyps united by 

 basal stolons; solitary forms have a stalked or wedge- 

 shaped base; neither skeletons nor basal suction 

 discs; many grow upon invertebrates. 



ORDER CERIANTHARIA (Tube Anemones) 



Diagnosis: solitary; polyps long, slender, and 

 anemone-like but never with a basal suction disc; 

 mostly burrowing forms in sand or mud; usually only 

 the tentacles and mouth are visible on the surface, 

 even when the animals are not disturbed; construct 

 black, often slimy, parchment-like tubes up to 6 or 

 more feet long. 



CTENOPHORA (Comb Jellies) 



Diagnosis: symmetry biradial, body more or less 

 spherical, the general appearance causing the com- 

 mon name "sea walnuts," but some are flat and belt- 

 like in appearance (Venus 's girdles); tissue grade of 

 organization, but muscles, digestive structures, and 

 a sensory body on top indicate more complex or- 

 ganization than in coelenterates; jellyfish-like and 

 semitransparent but have eight external rows of comb 

 plates and no stinging cells; body topped by a sense 

 organ and with mouth at the opposite end; strictly 

 free-swimming and marine (Figure 12.8). 



