522 TAXONOMY 



nial animals, as Obelia weismania. These animals reproduce by 

 buds, and by eggs and sperms. In the colonial types, certain 

 buds of the original colony are free-swimming jellyfish. These 

 produce the eggs and sperms. 



Class II Scyphozoa. Marine jellyfish, large in size. Ex- 

 amples are Aurelia flavidula and Portuguese man-of-war. 



Class III Anthozoa. Large hydra-like animals, single or 

 colonial, usually attached, with many tentacles arranged in 

 circles of multiples of five. The sea anemones and corals are 

 the best known examples. 



Phylum IV PLATYHELMINTHES (Gr., platys flat; hel- 

 minthos worm), or flatworms. Three-layered animals, bilat- 

 erally symmetrical, usually small, ribbon- or leaf-like, flat, and 

 live in water. Most flatworms are parasitic. Examples are 

 tapeworm and liver fluke. 



Phylum V NEMATHELMINTHES (Gr., nematos a 

 thread), or round worms. Three-layered, elongated, thread-like 

 animals, often parasitic. Vinegar eels, the horsehair worm, the pork 

 worm or trichina, the threadworm, and the hookworm are examples. 

 Phylum VI ECHINODERMATA (Gr., echinos hedge hog; 

 derma skin). Radially symmetrical, spiny-skinned animals 

 which live in salt water, more complicated in structure than the 

 worms. Five classes : 



Class I Asteroidea. Starfishes. 



Class II Ophiuroidea. The brittle stars or snake stars. 

 Class III Echinoidea. Sea urchins. 

 Class IV Holothuroidea. Includes the sea cucumbers. 

 Class V Crinoidea. Stone-like, deep-sea forms, now almost 

 extinct. Sea lilies and sea feathers are examples. 

 Phylum VII ANNELIDA (Lat., anellus a ring) . Bilateral, 

 segmented worms; composed of body rings or segments. The 

 digestive tract is a tube within a tubelike body. No jointed 

 appendages. There are two classes : 



