AJfj- 



what of the other types of coelenterates : the jellyfishes, corals, sea 

 firs (or hydroids), and sea pens? To look at, these animals represent 

 a very mixed group. They range from the stony coral to the saucer- 

 size jellyfish, which, when stranded on the shore, disintegrates 

 under the sun's rays into a patch of dried jelly. They also range 

 from the small mosslike growths known as sea firs to giant jelly- 

 fishes that measure more than seven feet across, with tentacles 120 

 feet long. Whereas the jelly layer in a sea anemone is thin, it forms 

 about 95 per cent of the total bulk of the jellyfish. Apart from their 

 great range in size, another difference among the coelenterates is 

 that the sea anemone and jellyfish are individual animals (known 

 as polyps), whereas a stony coral may be a colony of hundreds or 

 thousands of polyps weighing half a ton, all joined and working as 

 one to build a common skeleton. 



One reason why the coelenterates are so varied in appearance is 

 that, like plants, they have an infinite capacity for budding. The sea 

 fir starts as a larva that settles on a rock, then the larva turns into a 

 polyp on a stem. A bud appears on the stem and grows into a second 

 polyp, and on its stem another bud appears and forms a third polyp, 

 and so on. This continuous process of budding forms a complex of 

 stems and branches up to a foot high, crowded with polyps. 



Stony corals do much the same, except that each polyp lays 

 down a stony cup for itself, and the result is a huge stony mass like 

 the brain coral. Even jellyfishes pass through a similar stage when 

 the larva grows into an elongated polyp seated on a rock. The polyp 

 buds off small saucer-shaped jellyfishes, or medusae, each of which 

 swims away and grows into a mature jellyfish. 



Perhaps the most remarkable example of budding is seen in the 

 siphonophores, of which the Portuguese man-of-war is the most 

 familiar. Its larva grows into a hollow sack having one tentacle 

 beside the mouth opening. It then produces additional buds 

 that develop into specialized polyps - some for feeding, others for 



The sea anemone, also a coelenterate, is a 

 carnivorous animal low on the evolutionary 

 scale. Tentacles, w/hich are sensitive to 

 flavors and so detect food, surround ttie 

 opening to the stomach. This opening is also 

 used to eject vi/aste. Left: an early engraving 

 of open and partly open coral polyps. 



Unlike the solitary cup polyp, the polyps 

 forming the "brain" coral share a great 

 cluster of cups, resulting in the boulder like 

 formations that are the true reef builders. 



85 



