MONOCELLULAR ANIMALS -THE PROTOZOA 



129 





tl 





k 



dodcria 



Discorbis 



Oxnerellq Pencroplis 



Fig. 7-23. Various types of marine sarcodinids. 



at the bottom of the sea. While the globig- 

 erina ooze covers much of the ocean floor 

 and chalk has formed in some places, par- 

 ticularly along the shorelines, there has usu- 

 ally been a mixture of other deposits. Glo- 

 bigerina deposits appear in certain strata 

 of the earth's surface and have a definite 

 relation to the formation of petroleum. 

 Therefore, knowledge of foraminiferans has 

 been useful to geologists in predicting the 

 location of oil deposits. 



Parasitic amoebae. Some amoebae, like 

 some flagellates, have become adapted to 

 life in the body cavities of many different 

 animals, including man. Of the half dozen 

 or so amoebae that inhabit the various cavi- 

 ties of man, only one, Endameba histoly- 

 tica, causes any great harm. This amoeba is 

 responsible for the well-known amoebic 

 dysentery. Though not common in the pop- 

 ulation as a whole, it became an important 

 disease among our armed forces fighting in 



the tropics in the past war. Native villages 

 were often infected 100 per cent, providing 

 a rich source of parasites for spreading the 

 infection to newcomers. 



The parasites are transmitted from per- 

 son to person by contaminated food and 

 water (Fig. 7-24). There may also be an 

 indirect transfer by way of flies and other 

 insects that pick up the infective stages on 

 their feet and proboscis, carrying them di- 

 rectly to food and water. Hence, the obvious 

 method of control is to instigate sanitation 

 in respect to human excreta and to destroy 

 the flies. Both of these measures can easily 

 be accomplished in civilized communities, 

 but not among primitive peoples where 

 both the knowledge and the facilities are 

 lacking. 



Some notorious outbreaks of amoebic dys- 

 entery have occurred in the United States 

 which have been traced directly to faulty 

 plumbing. Studies among groups in re- 



