522 TAXONOMY 



nial animals, as Obelia weisinania. These animals reproduce by 

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

 buds of the original colony are free-swimming jelh^sh. 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 ariemones 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 

 liye 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 porl: 

 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 liye in salt w^ater, more complicated in structure than the 

 worms. Fiye 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. vStone-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 : 



