152 SYSTEMATIC ZOOLOGY. 



causing malaria. Mosquitoes in biting a malarial patient 

 take the parasite with the blood and can then infect 



FIG. 8. Four stages in the history of the Sporozoan which causes malaria. 

 In A a spore has just entered a blood-corpuscle; in B it has increased in 

 size ; in C it is beginning to break up into spores ; in D the spores are fully 

 formed. The blood-corpuscle now breaks up and the spores are set free to 

 enter other corpuscles. 



another person. More recently discovered is the Sporozoan 

 which lives in the tissue-cells and is the cause of the 

 disease smallpox. 



SUMMARY OF IMPORTANT FACTS. 



1. The PROTOZOA are microscopic animals, each con- 

 sisting of a single cell. 



2. They may possess cell-organs as pseudopodia, cilia, 

 flagella, cell-mouth, contracting vacuole. 



3. Each cell performs all of the functions of life; there 

 is no differentiation between the cells. 



4. The Protozoa reproduced by division. Incomplete 

 division may result in the formation of colonies. 



5. The Protozoa are divided into Rhizopoda, Infusoria, 

 and Sporozoa. 



6. The RHIZOPODA have no external cuticle, and con- 

 sequently may take food at any point of the surface. 

 They possess pseudopodia. Many form skeletons of lime 

 or silica. 



7. The INFUSORIA have a cuticle; in most there is a 

 cell-mouth for taking food. They have cilia, flagella, or 

 tentacles. 



