CLASSIFICATION OF LIVING THINGS 141 



Class 2. Mastigophora. Protozoa, generally of small 

 size, provided with one or more flagella. Euglena, 

 Peranema, Pandorina, Volvox. 



Class 3. Infusoria. Protozoa bearing cilia, with mouth 

 and contractile vacuole always present. Para- 

 mecium, Vorticella, Stentor, Colpoda. 



Class 4. Sporozoa. Parasitic protozoa without motile 

 organs in the adult; reproduce by spore formation. 

 Plasmodium. 



PHYLUM PORIFERA. Radially symmetrical animals, the 

 body wall containing many pores for the entrance 

 of water, and usually supported by a skeleton of 

 spicules. 



PHLYTJM CXELENTERATA. Radially symmetrical animals 

 with mouth and gastro-vascular cavity, but with- 

 out ccelom. Stinging cells present. 



Class 1. Hydrozoa. Ccelenterates with solitary or 

 colonial polyps, and with an alternation of gen- 

 erations. The medusae have a velum. Hydra, 

 Pennaria, Obelia, Gonionemus. 



Class 2. Scyphozoa. Ccelenterates of considerable size, 

 the medusa prominent but the polyps much re- 

 duced or absent. The edge of the bell is lobed and 

 a velum is not present. Aurelia, Cyanea. 



Class 3. Actinozoa. Polyps solitary or colonial, with 

 esophageal tube and mesenteric folds. A medusa 

 generation is entirely lacking. Sea anemones and 

 corals. 



PHYLUM ECHINODERMATA. Radially symmetrical ani- 

 mals usually with a pentamerous arrangement. 

 Mouth and anus present, ccelom well developed, 

 a water vascular system. The body wall con- 

 tains calcareous plates and usually bears spines. 



