ECTOPARASITIC INFUSOEIA 91 



which vary in number and arrangement. 1 For further details the 

 student is referred to the special literature on the subject. 



The caecum of the horse is also the habitat of a large variety of 

 Infusoria, which, in many cases, resemble those described above. To 

 obtain the Infusoria in a medium of suitable fluidity, the bowel- 

 contents should be filtered through a warm cloth. The parasites 

 are, however, more sensitive than those found in the stomach of 

 ruminants and, even with the aid of a thermostat, it is not possible 

 to keep them alive for longer than two or three hours. The species 

 most frequently met with, which is also the largest, is Cycloposthium 

 palmatus. It is characterized by a remarkable double organ of move- 

 ment ; a bunch of six strong cilia, which proceed from a short tube- 

 like sheath, is placed upon either side at the hinder end of the body. 

 Other varieties, together with their more intimate structural details, 

 are described by Bundle. 2 



(d) Ectoparasitic Infusoria of Fish. 



Infusoria are frequently found upon the skin and gills of fresh- 

 water fish, and in fishes and aquaria these may have a pathogenic 

 significance. The most interesting varieties and the ones most 

 frequently met with are Cyclochceta domerguei, Wall., a semicircular 

 Infusorian of the order Peritrichida, found upon the gills, to which it 

 attaches itself by means of its modified and sucker-like peristome ; 

 and Ichthyophthirius multifilius, Fouqu,, a nearly round and almost 

 opaque Holotrichian, which forms small white pustules under the 

 epidermis. It encysts after the bursting of the pustules and the cysts 

 fall to the bottom of the water, where numerous daughter-cells are 

 formed within the cyst. Both of these parasites may be fixed in 

 cover-glass specimens by the method described for Costia (see p. 41). 



1 A. Schuberg, " Die Protozoen des Wiederkauermagens," Zool. Jahrb. Abt. /. 

 Syst., vol. iii, 1888, pp. 364-418 ; A. Schuberg, " Ueber einige Organisationsverhalt- 

 nisse der Infusorien des Weiderkauermagens," Sitzber. d. phys-med. Ges Wiirzburff, 

 November 21, 1891 ; E. Eberlein, " Ueber die im Wiederkauermagen vorkomraenden 

 ciliaten Infusorien," Zeitsclir. f. wiss. "ZooL, vol. lix, 1895, pp. 232-304. 



2 A. Bundle, " Ciliate Infusorien in Caecum des Pferdes," Zeitsch. f. iviss. Zool., 

 vol. Ix, 1895. 



