124 



COLLEGE ZOOLOGY 



crowns of various colors, resemDiing not so 

 much the anemones after which they were 

 named, but more closely chrysanthemums or 

 dahlias. When greatly disturbed, these sensi- 

 tive "flowers" may be drawn into a shape- 

 less mass, and the long white acontia threads 

 bearing stinging capsules are extended 

 through minute pores in the body wall to 

 drive away enemies. 



In their natural habitat, sea anemones are 

 far from flowerlike. They serve as death traps 

 for any small animal that comes within 

 reach of their tentacles. They may be beauti- 

 ful in color but they wield their batteries of 

 stinging capsules with deadly effect. The 

 paralyzed prey is carried through the greedy 

 mouth, down the gullet, and into the en- 

 teron, which is hardly more than a digestive 

 sac. The food is digested by enzymes se- 

 creted by the cells of the digestive filaments 



and absorbed by the gastrodermis. Undi- 

 gested wastes are ejected through the 

 mouth. Saville-Kent's anemone, which lives 

 on the Great Barrier Reef of Australia, is 

 two feet across and is inhabited by small 

 red and white fish; these swim in and out 

 through the mouth without being injured 

 in any way by the stinging capsules. 



Astrangia— a coral polyp 



Astrangia danae is a white coral polyp 

 that inhabits the waters of our north Atlan- 

 tic coast. Another species, Astrangia insig- 

 nifica, occurs along the Pacific Coast; the 

 polyps of this species are orange and the 

 coral is red. A number of individuals live 

 together in colonies attached to rocks near 

 the shore. Each polyp looks like a small sea 

 anemone. Each polyp secretes a calcareous 



Figure 62. Colony of Astrangia which hves in the waters of the north Atlantic Coast. These 

 corals secrete protective limestone cups into which the delicate polyps can retract. (Courtesy of 

 George G. Lower.) 



skeleton within which the animal rests. The 

 corals on display in all museums are simply 

 skeletons of coral polyps. Although Astran- 

 a cuplike skeleton less than Vi 



gia builds 



inch in height, it produces large masses ot 

 coral in the course of centuries. The physio- 

 logic processes of corals are much like those 

 of other coelenterates. 



