184 ESSENTIALS OF BACTERIOLOGY 



containing 500 species; (3) infusoria, containing 700 species; 

 (4) sporozoa, containing 300 species. 



Sarcodina are chiefly marine forms, with processes change- 

 able in shape. 



Mastigophora have undulating flagella, and are known as 

 flagellates; to this division the trypanosomata belong. 



Infusoria have fine ciliary processes or numerous delicate 

 flagella. 



Sporozoa have no motile organs, and are reproduced by spores. 

 To this division belong the coccidia of malaria and the organ- 

 isms discovered by Mallory in scarlatina. 



Fig. 113. Pure culture of trypanosomes of mosquitoes Crithidia fas- 

 ciculata. Part of roset of elongated crithidia with flagella directed centrally 

 (Gen. 39, Xisoo) (Novy, MacNeal, and Torrey). 



Life-cycle. The complete cycle of reproduction has been 

 observed in only one of the pathogenic protozoa, namely, the 

 protozoa of malaria. 



Life Cycle of the Malarial Sporozoa. According to its 

 situation, the parasite exhibits two distinct phases of existence: 

 in the human blood it passes through an asexual reproductive 

 cycle, known as schizogony, while in the body of the mosquito 

 it undergoes an entirely different series of sexually reproductive 

 changes, called sporogony. It is simpler first to describe the 



