240 CLASSIFICATION OF PLANTS AND ANIMALS 



Class III. Anthozo'a. Hydra-like animals, usually attached, with many tentacles, disposed 

 in circlets in multiples of five. They may be single or colonial. The sea anemones and 

 corals (which form a skeleton usually of a living substance) are the best known examples. 



Ctenophora (te-n6f'o-ra), or sea walnuts, well known along our eastern coast, are sometimes 

 given as a separate phylum and sometimes as a class of the coelenterates. 



Obelia 



Amelia 

 Coelenterata. 



Sea anemone 



IV. Platyhelmin'thes (Gr. platys, flat; helminthos, worm), or flatworms. — 

 These are usually small, ribbon- or leaf -like and flat, and live in water. Most 

 flatworms are parasitic, examples being the tapeworm and liver fluke. There 

 are about 5000 known species. 



V. Nemathelmin'thes (Gr. nematos, a thread), or roundworms. — Three- 

 layered, elongated threadlike animals, often parasitic. Vinegar eels, the horse- 

 hair worm, the pork worm or trichina, and the dread hook- 

 worm are examples. About 15,000 species are known. 



Tapeworm. The 

 head (h) is shown 

 greatly magnified at 



Trichina. 



Sandwormi Leech 



Annulata. 



There are several classes of these worms and also at least four other phyla of small wormlike 

 creatures which it is not the province of an elementary book like this to describe. There are 

 perhaps 19,000 described species in these groups. If you are interested in knowing more about 

 their structure and names, look up a good book on classification, such as Parker and Haswell's 

 Zoology. 



