COASTLINES 



this for several years — as though nature had made a 

 mistake and the creature was destined to end its hfe as a 

 carnivorous underwater plant, quite unlike its parents. 



But at last the ''plant" begins to throw off dozens of 

 small transparent discs, none of them as large as rain- 

 drops. Each of these is a freely-swimming jelly-fish, com- 

 plete with a fringe of microscopic tentacles — a tiny disc 

 that pulsates rhythmically as it swims. 



Most of the larger jelly-fish are the medusa-stage of the 

 Coelenterate class Scyphozoa. Our description of the 

 life-cycle of one applies to one species of Amelia, but 

 there are Aurelia of many kinds and sizes. There is, for 

 instance, the large jelly-fish common to the coast of New 

 England, Aurelia flavidula, which sometimes reaches a 

 diameter of ten inches. All the Aurelia are miniature 

 umbrellas, but the Aurelia flavidula is one of the ornate 

 ones, with ornamental additions of its own. Its convex 

 body is smooth on its upper surface, while four thick 

 lobes hang from it which unite to form the creature's 

 mouth, also giving off four tentacles. The margin of the 

 "umbrella" is fringed and carries eight eyes, each covered 

 by a lobe. Just under the surface are the water-vascular 

 canals, radiating from the stomach. When in motion, the 

 entire ''umbrella" contracts and expands rhythmically 

 at an average rate of twelve to fifteen pulsations a 

 minute. 



A less common jelly-fish on the coast of New England 

 and in some parts of the North Atlantic is the monstrous 

 Cyanea arctica, or "blue jelly", which sometimes grows to 

 three or four feet in diameter, and has long tentacles 

 (sometimes extending to lOO feet) filled with stinging 

 lasso-cells which are poisonous to fishermen and bathers. 

 In exceptional circumstances the Aurelia do not pass 

 through the intermediate "plant-like" stage, but develop 

 their true jelly-fish characteristics more directly. The 

 Hydrozoa are more numerous in tropical seas, where they 

 comprise forms of extraordinary beauty and coloration. 



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