CHAPTER XVIII 



INTESTINAL SARCODINA IN GENERAL 



By 



Robert Hegner 



The Johns Hopkins University School of Hygiene and 



PubHc Health 



Although the members of four of the orders belonging to the 

 class SARCODINA are almost all free living, a large number of 

 species of amoebae occur in the fifth order, the amcebida. General 

 surveys of the class are to be found in Calkins' Biology of the 

 Protozoa, pp. 313-341, in Wenyon's Protozoology, pp. 160-267, 

 and in Hegner and Taliaferro's Human Protozoology, pp. 19-20. 

 Calkins also gives a key to the genera of the sarcodina on pages 

 341-362. Calkins' account is largely devoted to free-living species 

 whereas Wenyon and Hegner and Taliaferro emphasize parasitic 

 species. 



The order heliozoa contains protozoa commonly known as sun 

 animalcules, most of which live in fresh water. Parasitic species, 

 however, occur in several genera, for example, Vampyrella which 

 is parasitic on algae and Nuclearm which is parasitic in both algae 

 and protozoa. To the order radiolaria belong large numbers of 

 marine protozoa that possess shells. Many of them have in their 

 protoplasm vegetable organisms about fifteen microns in diameter 

 with a cellulose wall. These are known as zooxanthell^ which 

 are supposed to be symbiotic. A number of common fresh-water 

 protozoa, such as Arcella and Difflugia, occur in the order fora- 

 minifera; others, especially the most complicated species, are to 

 be found in salt water. Species belonging to several genera have 

 been cultivated from the feces of man, horse and pig. Belar 

 (1921) recognizes six species in the genus Chlamydophrys. C. ster- 

 corea appears to be the most common. To obtain organisms of this 

 type one should place pig's feces in a Petri dish in a moist cham- 



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