308 GENERAL ZOOLOGY 



Phylum III. Coelenterata : radially symmetrical, two cell layers, ten- 

 tacles with stinging cells, with a single cavity serving 

 as both digestive cavity and body cavity. 

 Class 1. Hydrozoa: usually two forms — polyp and medusa, 

 the former with no folds in endoderm. Ex. 

 Hydra viridissima. 

 Class 2. Scyphozoa: usually polyp and medusa, of which 

 latter is larger, former with four folds in en- 

 doderm. Ex. Aurelia flavidula. 

 Class 3. Anthozoa: polyp only, endoderm with many 

 folds. Ex. Metridium marginatum. 

 Phylum IV. Ctenophora: similar to medusa with eight bands of cilia 

 for locomotion, but a single pair of tentacles. Ex. 

 Pleurobrachia pileus (sea comb) . 

 Phylum V. Plathelminthes (flatworms) : body flat, bilaterally sym- 

 metrical, no body cavity. 

 Class 1. Turbellaria: free-living, body covered with cilia. 



Ex. Procotyla fluviatilis. 

 Class 2. Trematoda (flukes) : always parasitic, digestive 



tract present. Ex. Fasciola hepatica. 

 Class 3. Cestoda (tapeworms) : always parasitic, no diges- 

 tive organs. Ex. Taenia saginata. 

 Phylum VI. Nemathelminthes (roundworms) : round, not segmented, 

 with a digestive system and a body cavity. 

 Class 1. Nematoda: characters as for phylum. Ex. 

 Ascaris lumbricoides. 

 Phylum VII. Trochelminthes (wheel animalcules) : many-celled, minute, 



with wheel of cilia about mouth. 

 Class 1. Rolifera: characters as for phylum. Ex.Hydatina. 

 Phylum VIII. Annelida (jointed worms) : body segmented, with dis- 

 tinct body cavities. 

 Class 1. Chsetopoda: bristles for appendages. Ex. Lum- 



bricus terrestris. 

 Class 2. Hirudinea (leeches) : no bristles. Ex. Placob- 

 della rugosa. 

 Phylum IX. Molluscoidea: with a crown of ciliated tentacles on an- 

 terior end of body. 

 Class 1. Bryozoa (moss animals) : usually colonial, diges- 

 tive system complete. Ex. Plumatella. 

 Phylum X. Echinoderma : radially symmetrical, with body cavity, 

 locomotion usually by tube feet, limy plates in skin. 

 Class 1. Asteroidea (starfishes) : a central disk with five 

 or more arms, body cavity extending into 

 arms. Ex. Asterias vulgaris. 



