414 VETERINARY BACTERIOLOGY 



The life histories of the various protozoa show such com- 

 plexities that they may better be treated under the separate sub- 

 divisions. 



Classification of the Protozoa. Authorities are not in entire 

 accord with reference to the principal subdivisions of the protozoa. 

 The classes here used are those given by Calkins in " The Pro- 

 tozoa." The definitions of the groups here given will not hold in 

 all cases for non-parasitic forms. 



CLASSES OF PROTOZOA 



A. Motile in adult life by means of pseudopodia. Reproduc- 

 tion by simple division and by spore formation. I. Sarcodina or 

 Rhizopoda. 



B. Not possessing pseudopodia in the adult form. 



(1) Adult motile by means of 



a. Flagella. With one nucleus. II. Mastigophora. 



b. Cilia. Two types of nuclei. III. Infusoria or Cilio- 

 phora. 



(2) Adult forms non-motile. Reproduction by spores. 

 IV. Sporozoa. 



Pathogenic organisms belonging to each of the.four classes are 

 known. These will be treated under separate chapters. 



