PROTOZOA 377 



Classification of Protozoa. In the classification of pro- 

 tozoa their morphology and their physiology are considered. 

 Physiologically, they are grouped according to their ability 

 to exist on dead or living organic matter into saprophytic and 

 parasitic forms. The parasitic forms of the protozoa are again 

 divided into commensals and pathogenic forms. The classifi- 

 cation of protozoa morphologically is still in an unsettled 

 stage. New discoveries are being made that result in constant 

 changes in their classification. The following classification 

 of protozoa is taken from Park's work, Pathogenic Bacteria 

 and Protozoa, and is practically the same as Calkin's clas- 

 sification given in Osier's Modern Medicine. In the fur- 

 ther discussion only those forms pathogenic for domesticated 

 animals with brief references to a few affecting man will be 

 considered. 



CLASSIFICATION. 



Phylum. Protozoa. Unicellular animal organisms which reproduce 

 by division or spore-formation; solitary or united in colonies; 

 free-living or parasitic. 



Sub-Phylum I. Sarcodina. Protozoa with changeable protoplas- 

 mic processes or pseudopodia. 

 Class I. Rhizopodia. Sarcodina with pseudopodia in the form 



of lobose or reticulose processes, with or without shells. 

 Sub-class. Amoebida. Pseudopodia lobose. 

 Order 1. Gymnamoebida. Naked amoeboid forms with 

 lobose pseudopodia. Here are placed a few parasitic 

 forms belonging to the genera Amoeba, Entamoeba, and 

 Leydenia. 



Order 2. Thecamoebida. Shell-bearing amoeboid forms with 

 lobose pseudopodia. One parasitic form, genus Allo- 

 gromia, is placed in this order. 



Sub-class. Foraminifera. Divided into 10 orders; the various 

 genera are salt water forms for the most part and are 

 rarely parasitic. 



Sub-class. Mycetozoa would be placed here were we to con- 

 sider these forms as protozoa instead of fungi. Here are 

 placed parasitic forms such as Plasmodiophora, Tetra- 

 myxa, Labyrinthula, and Nucleophaga. 



