224 RESEARCH IN PROTOZOOLOGY 



infected. How many species of this genus occur in frogs it is 

 difficult to state. A careful study of the genus should be made. An- 

 other species, A^. ovalis, occurs frequently in the common cock- 

 roach and in the mole cricket. 



To the order oligotrichida belong a number of ciliates that 

 occur in the stomach of cattle, in the cecum of the horse, in the 

 cecum of wild guinea-pigs, in the intestine of the chimpanzee and 

 gorilla and in the intestine or cecum of certain other mammals. 

 In this order belong the common genus Diplodinium which was 

 described in detail by Sharp (1914) and Troglodytella which was 

 first described by Brumpt and Joyeux (1912) from the chimpan- 

 zee. The latter is one of the few protozoa of monkeys that has 

 not been found in man (Hegner, 1928). 



The order hypotrichida contains comparatively few parasites. 

 These usually creep about on the surface of aquatic invertebrates. 

 One of the best known species is Kerona pediculiis which Uhle- 

 meyer (1922) has shown to be an obligate parasite. 



There are also comparatively few parasites among the peri- 

 TRiCHiDA. A number of species of the vorticellid^ attach them- 

 selves to aquatic animals and may be considered parasitic in the 

 broad sense of the term. Others, such as Spirochona, occur on the 

 gills of the fresh-water crustacean Gammarus. The species most 

 easily obtained for study is Trichodina pcdlculus which creeps 

 about on the body of fresh-water hydra or tadpoles, and other 

 aquatic animals. Another ectoparasitic peritrich is Cyclochceta 

 which lives on the skin of fish. 



Most of the sucTORiA attach themselves to aquatic plants, to 

 animals, particularly small Crustacea, and insect larvae. All de- 

 grees of parasitism are exhibited by members of this group. Cer- 

 tain species attach themselves to almost any object, either living 

 or lifeless; others commonly are found attached to plants; some 

 prefer snails, others protozoa, water insects, hydroids or Crus- 

 tacea ; in some cases any part of the body of the host is apparently 

 satisfactory but frequently only one particular region is selected. 

 Certain members of the group actually parasitize other protozoa. 

 The SUCTORIA are thus seen to vary greatly in their host-parasite 

 relations. 



