X 



Host-Parasite Relationships 



Parasitism 



Types of parasites 



Commensalism as an evolutionary goal 



Symbiosis 



The evolution of parasites 



Host-specificity 



Taxonomic distribution of parasitic Pro- 

 tozoa 



Protozoa as hosts 

 Protozoan parasites of Protozoa 

 Bacterial parasites of Protozoa 

 Other plants as parasites of Protozoa 



Infections 



Transfer of parasitic Protozoa 



Geographical distribution of parasites of 

 man 

 The Americas 

 The Mediterranean area 

 Europe north of the Mediterranean area 

 Central and southern Africa 

 Southern and southeastern Asia 

 The Pacific area 



Literature cited 



PARASITISM 



Xrotozoa which HAVE become adapted to life in or on the body 

 of another organism, the host, are commonly referred to as parasites. 

 Parasitism, in a correspondingly broad sense, designates the association 

 of such a parasite with its host. This is also the original meaning of 

 symbiosis, as proposed by de Bary,i but recent usage has generally re- 

 stricted this term to the special relationship of "mutualism" (van 

 Beneden). Since the problematical benefits of revising accepted termi- 

 nology probably would not balance the resulting misunderstandings, 

 the prevailing usage will be followed here. 



Types of parasites 



Protozoa which normally live on the surface of the host's body 



may be called ectoparasites — or ectocommensals, if they neither damage 



nor benefit the host. Ectocommensalism, obviously limited to aquatic 



hosts, may involve definite attachment of the commensal or merely the 



^A concise historical discussion of terminology has been published by Kirby (56). 



527 



