PARASITIC INFUSORIA IN GENERAL 223 



of the order holotrichida or in the group protociliata, depend- 

 ing on opinion. All of the members of this family are parasitic. 

 The best account of the group is contained in ]\Ietcalf's (1923) 

 monograph on the Opalinid Cilmtc Infusormns. Problems and 

 methods of study of this family are presented by Metcalf in Chap- 

 ter XX\^I. These ciliates, as Metcalf shows, are very easily ob- 

 tained from the rectum of frogs and other amphibia and ofifer 

 many interesting and important problems for study. 



The order holotrichida contains many species of parasitic 

 ciliates. All of the species belonging to the suborder astomatea 

 are parasitic in habit, living principally in the intestine and body 

 cavity of invertebrates. A number of species have been described 

 from the intestine of earthworms. Some of these are known by the 

 writer to occur in the earthworms of Baltimore. A species belong- 

 ing to the genus IntosheUina has been reported from the fresh- 

 water worm, Tuhifcx, and a species of Haptophrya, H. michi- 

 gancnsis, has recently been described from the intestine of a newt 

 in Alichigan (Woodhead, 1928). A species belonging to the genus 

 Cepedella occurs in the liver of cyclad molluscs of the genus 

 Sphcer'min. Considerable information is available regarding Col- 

 linia branchiannn which is parasitic in the body cavity of Gam- 

 marus pulex. Whether this and other species that have been 

 recorded from the body cavity and intestine of various inverte- 

 brates occur in this country is not known. 



The suborder stomatea contains a large number of interesting 

 species. Several of these belong to genera such as Chilodon, Col- 

 poda and Uroncma that have been reported from human feces and 

 have been considered by some as human parasites. These should, 

 however, be classed as coprozoic species. The interesting ciliate 

 Ichthyophthirms multifilus that Hves in the skin of fishes belongs 

 in this suborder. Many species of stomatea have been reported 

 from the cecum of the horse, from the cecum of wild guinea-pigs 

 and from the rumen of cattle and sheep. 



To the order heterotrichida belong two genera of great in- 

 terest. These are NyctotJicrus and Balantidiiiui. The genus Balan- 

 tidium is considered in Chapter XXV. Several species of Nyc- 

 t other us have been described from man but these, if they really 

 belonged to this genus, were probably coprozoic forms. Species of 

 Kyctothcms from animals are easy to secure. A^ cordiforinis is 

 present in the rectum of frogs, a large percentage of which are 



