The Protozoa 45 



CLASSIFICATION OF THE PATHOGENIC PROTOZOA 



Phylum PROTOZOA (jrpSros first, fwoc animal). Unicellular animal 

 organisms. 

 Class Rhizopoda (/Sifa root, irwdos foot). Having soft plasmic bodies 

 with or without external protecting shells. The contour 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 (7u/i>i6s naked). Rhizopoda without external 

 shells or coverings. 

 Genus Amoeba {a/ioi^a to change). 

 Genus Entamoeba. 

 Genus Chlamydophrys. 

 Genus Leydenia. 

 Class Mastigophora (iiaariyos wnips, <^opos to bear). Organisms of 

 well-defined form, naked or surrounded by a well-defined membrane. 

 Nutrition is holozoic, holophytic, parasitic, or saprophytic. Mouth, 

 contractile vesicle, and nucleus usually present. 

 Order Flagellata (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, holophytic, parasitic, or saprophytic. 

 Family Cercomonida. Body pyriform with several anterior flagella 

 and an undulating membrane. 

 Genus Cercomonas. 

 Genus Trichomonas. 

 Genus Monas. 

 Genus 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). 

 Family Trypanosomidm. Body delicately fusiform. Contains a 

 nucleus, a blep? aroplast or centrosome, and an undulating mem- 

 brane. A single wavy flagellum arises in the posterior part 

 of the body close to the centrosome, passes along the edge of the 

 undulating membrane to the anterior extremity, where it continues 

 free for some distance. Nutrition parasitic. Reproduces by 

 division. 

 Genus Trypanosoma. 

 Genus Leishmania. 

 Genus Babesia. 

 Family Spirochcetida. Organisms very long and spirally twisted. 

 Nucleus indistinct. Multiplication probably by longitudinal 

 division only. Nutrition is parasitic or saprophytic. 

 Genus Spirochaeta. Body flattened, with a very narrow undulating 



membrane. 

 Genus Treponema. Body not flattened. No undulating membrane. 

 Extremities sharp pointed and terminating in short flagella. 

 Class Sporozoa (o-iropos a spore, ftiov an animal). Organisms unprovided 

 with cilia or flagella in the adult stage. Always endoparasites in the 

 cells, tissues, or cavities of other animals. Nutrition is parasitic and 

 osmotic. Reproduction always by spore-formation, the sporozoites 

 either being produced by the parent or indirectly from spores, into 

 which the parent divides. 

 Subclass Telosporidia. Spore-formation ends the individual life, the 

 entire organism being transformed to spores. 

 Order Gregarinida. Possess distinct membrane with myonemes 

 during adult life; locomotion mainly by contraction. Young stages 

 alone (cephalonts) are intracellular parasites, the adults (sporonts) 

 being found in the digestive tract or the body cavities. Sporulation 

 takes place after or without conjugation, but within a cyst that is 

 never formed, while the parasite is intracellular. 



