24 RESEARCH IN PROTOZOOLOGY 



hypotrich and ride around on it. Like K. pediculus it is also com- 

 monly referred to as the polyp louse. 



Ordinarily this protozoon merely uses its host as a means of 

 transportation or as a place of rest; it is probable, though, that 

 some irritation is caused to very soft-skinned hosts and thus 

 abrasions may be made which would enable bacteria or fungi to 

 enter. If the cihates become very numerous they might produce 

 death by suffocation. 



Description: Diameter and length about 70/i; hour-glass-shaped; found 

 living commensally on various aquatic animals. 



Some other species of Trichodma that have been reported are: 

 T. haltica Quennerstedt, 1869, a marine form from Neritina 

 Uuviatilis, T. digitodiscus Stein from hydras, T. labrorum Chatton, 

 1910, from the gills of fresh-water fish, T. mitra (Stein, 1854) 

 von Siebold, from planarians, and T. patcllcu Caullery and Mesnil, 

 191 5, from the gills of molluscs. There is a symbiotic alga asso- 

 ciated with this species. T. scorpcnce Robin, 1879, has been de- 

 scribed from the gills of fish. According to Robin these ciliates 

 quickly die if removed from their host. T. steini Claparede and 

 Lachmann, 1858, was found on fresh- water planarians. Kepner 

 and Pickens (1925) have pointed out that the complex adaptive 

 structures in the basal disc of T. sfcini are but the homologues of 

 similar structures found in Vorticclla. Accordmg to these authors 

 Trichodina has undergone a reversal of polarity. T. synaptce 

 Cuenot has been reported from echinoderms, and T. urinicola Ful- 

 ton, 1923, from the urinary bladder of amphibia. 



(c) Trichodinopsis paradoxa Claparede and Lachmann. 



Claparede and Lachmann (1858) described this peculiar peri- 

 trichous ciliate from the respiratory surfaces and intestines of 

 Cyclostoma elegans. It closely resembles Trichodina except for the 

 fine cilia which cover its surface. According to Faure-Fremiet 

 (1909) this organism is the same as Trichodina pcdicidus, but it 

 lives in constant symbiosis with an ectoparasitic spirillum (the 

 fine surface cilia) and an internal bacterium. 



Description: Length when extended 130/1 lives on respiratory surface and 

 in intestine of molluscs ; possibly identical with Trichodiim pediculus. 



General biology and morpJiology: Naturally most articles deal 

 more or less with the biology and morphology of the organism 



