COELENTERATA 61 



hang short pale green streamers. These circular 

 discs are sometimes found in great numbers washed 

 on the beach after storms. After the storm of Sep- 

 tember, 1930, a great many living animals were 

 found on the beach at Cape May. 



SCYPHOZOA 



To this group belong the larger jelly-fish or 

 medusae. Although usually larger than the Hydro- 

 zoan medusae, they have roughly the same structure. 

 They are umbrella-shaped and from the center of the 

 umbrella hangs the stalk-like manubrium containing 

 the mouth and stomach. From the manubrium 

 radiate numerous canals. The velum or veil is 

 usually absent ; tentacles are present in most species. 

 Like the hydromedusae, these jelly-fish are equipped 

 with great quantities of stinging cells or nemato- 

 cysts. Sometimes these animals are so abundant as 

 to render ocean bathing very unpleasant if not 

 actually dangerous. 



The alternation of generations, characteristic of 

 the Hydrozoa, is reduced or absent in the Scyphozoa. 

 The hydroid stage when present is very minute. 

 The egg develops into a planula, a sphere-like form, 

 which swims freely for while. After the free-swim- 

 ming period, the little creature attaches itself to 

 some solid object, The planulae of some species grow 

 into hydroids; in other species the attached planula 

 grows in a different manner, constricting at intervals, 

 and at maturity resembles a pile of inverted saucers 

 (strobila stage). Each of these saucers becomes de- 

 tached and is known as an ephyrula and develops 

 into an adult medusa. A few species mature directly 

 from the egg without any intervening stage. 



