The Protozoa 51 



THE PROTOZOA. 



The protozoa are unicellular animal organisms as differen- 

 tiated from the metazoa which are multicellular animal or- 

 ganisms. The restriction, implied by the term unicellular is, 

 however, too narrow, for there are colonial protozoa that con- 

 sist of many cells, yet share other protozoan characters. 



For the purposes of this work, however, all protozoa are 

 to be regarded as unicellular and the individuals independent 

 of one another. 



Classification. Many schemes have been devised for 

 systematically arranging the protozoa, that which follows 

 being an abbreviation of the standard classification, made to 

 correspond with the requirements of this work that deals 

 only with the pathogenic forms. 



CLASSIFICATION OF THE PATHOGENIC PROTOZOA. 



Phylum PROTOZOA (Trpwrof first, Cwov animal). Unicellular ani- 



mal organisms. 



Class Rhizopoda (pifa root, 7rw(5of foot). Having soft plasmic 

 bodies with or without external protecting shells. The con- 

 tour subject to change through the formation of extensions 

 known as pseudopods. These may be blunt, rounded, or 

 lobose, filamentous, or anastomosing. The nutrition is 

 holozoic or holophytic. 

 Order GYMNAMCEBA (yvfj.v6c naked). Rhizopoda without ex- 



ternal shells or coverings. 

 Genus Amoeba (a^oifta to change). 

 Entamoeba. 

 Chlamydophrys. 

 " Leydenia. 



Class Mastigophora (udanyos whips, <t>6poc to bear). Organ- 

 isms of well-defined form, naked or surrounded by a well- 

 defined membrane. Nutrition is holozoic, holophytic, para- 

 sitic, or saprophytic. Mouth, contractile vesicle, and nucleus 

 usually present. 



Order FLAGEXLATA (Latin, flagellare, to beat). Small organisms 

 with a well-defined mononucleate body, at the anterior end 

 or both ends of which are one or more flagella. Actively 

 motile. May become encysted. Nutrition is holozoic, holo- 

 phytic, parasitic, or saprophytic. 

 Family CercomonidcB. Body pyriform, with several anterior 



flagella and an undulating membrane. 

 Genus Cercomonas. 

 " Trichomonas. . 

 Monas. 

 Plagiomonas. 



Family Lambliadce. Body pyriform, very much attenuated 

 behind. Ventral surface shows a reniform depression, 

 about the posterior part of which there are six flagella. 

 There are also two flagella at the posterior extremity. 

 Genus Lamblia (Megastomum). 



