62 HYDR^, JELLYFISHES, SEA ANEMONES, CORAL POLYPS 



eye. Because of the alternate lateral branching of the 

 vertical stems, the animal shows a striking resemblance to 

 a plant. 



Usually, near the base of the vertical stem bearing the 

 zooids will be found one or more club-shaped cavities, 

 formed at the ends of short lateral branches. These cap- 

 sules are closed at the free ends and contain within them the 

 reproductive zooids (Fig. 18, rp). While within the trans- 

 parent capsule the reproductive zooids are mere buds and 

 are called medusa buds. After a time the capsules break 

 open and the medusa buds pass out, one by one, and are 

 then known as medusas, and sometimes jellyfish. They 

 are umbrella-shaped and are found floating with the convex 

 side uppermost. 



After a time these medusae produce eggs that finally 

 develop into the plantlike, colonial organism with which 

 we started. 



Jellyfishes 



Olass II. — Scyphozoa {cuplike animals) 



Nearly all of the large jellyfishes belong to this class 

 and, in general, it may be said that the members of 

 this class are larger than those of the Hydrozoa. Moreover, 



the majority of 



the Scyphozoa swim 



freely on the surface 



of the ocean. A 



few are found to 



inhabit the ocean 



FiQ. 19.— Jellyfish (4 urcZia). at great depths. 



The common jellyfish, Aurelia. — This is a true jellyfish 



and has a convex, tough, jellylike body and is often found 



