ONE-CELLED ANIMALS— PHYLUM PROTOZOA 



95 



Practically all of the organisms will have migrated to this area, and 

 their combined bodies will give the green color to the spot. 



Euglena lives in fresh-water ponds and streams and carries out its 

 respiration and excretion in the same manner as the amoeba. It also 

 has a contractile vacuole located near the flagellum which expels 

 excess water. It reproduces by longitudinal fission. 



During recent years we have heard much about the "red tide" along 

 the western coast of Florida. When viewed from the air, large areas 

 of the water can be seen to have a brownish-red tinge, and within this 

 area there may be millions of dead fish. Many of these are washed 

 up on the beaches and create a serious problem of disposal. An 

 analysis of the water in such areas has shown a heavy concentration 



Courtesy Army Inst, of Pathology 



Fig. 7.7. A person with an advanced case of African sleeping sickness. 



of a marine protozoan, Gymnodiniitm brevis, which is in the class Masti- 

 gophora. A quart of water taken from this area will contain as many as 

 60,000,000 of these small animals. When so abundant, the waste prod- 

 ucts from these organisms cause the surrounding water to become thick 

 and slimy, and fish cannot survive in it. The "red tide" appears when- 

 ever certain conditions prevail that are very favorable to the growth of this 

 protozoan. The red color is due to pigmented bodies within the cells. 

 It is estimated that half a billion fish were destroyed in this way along 

 Florida's west coast in 1947. 



Some of the Mastigophora invade the blood stream of higher animals 

 and cause serious diseases. Among the many scourges of humanity to be 

 found in Africa is the dread disease of African sleeping sickness. This 

 disease is generally caused by Trypanosoma gambiense, one of the Masti- 

 gophora that lives in the blood stream of man. It is spread through 

 the bite of the tsetse fly, a blood-sucking insect which is very abundant in 

 many sections of Africa. Death usually terminates untreated cases of 



