SPECIAL MORPHOLOGY AND TAXONOMY OF LXFUSORIA 373 



region are able to take in living organisms even larger than them- 

 selves (see p. 17s and Fig. 161). 



In Siictoria, food-taking is of an entirely different type. Mouths 

 are absent but food may be taken in through any one of the many 

 suctorial tentacles. The body wall of a captive organism is cyto- 

 lyzed at the point where the tentacle is in contact and the endoplasm 

 of the prey either passes in a stream through the lumen of the 

 tentacle, or the endoplasm of the captor enters the body of the 

 victim and digests its endoplasm in situ (Maupas, 1883). Ten- 

 tacles for adhesion are also present in Mesodinunn (Fig. 163). 



While the vast majority of Infusoria are holozoic in food-getting, 

 parasitic types may be holozoic, or saprozoic (OpoUna). Proteins 

 are digested by all and carbohydrates in some {Balantidmm, 

 Glaessner, see p. 186). 



Parasitism in Infusoria, as in other great groups of Protozoa, is 

 widely spread and some of the adaptations to this end merit special 

 consideration. The majority are apparently harmless commensals 

 of digestive tract and body cavity; some, however, are more serious, 

 Balantidium coli for example, causing acute enteritis in man and 

 other mammals. Fctoparasitic forms may also be a source of 

 trouble. Amphilcptus hranchiarum gets under the gill mantles of 

 tadpoles and ingests groups of epithelial cells (Wenrich) ; others form 

 peculiar arms by which they are anchored to gill bars {Ellobiophrya 

 donacis, Chatton). In the main related forms are not strictly 

 parasitic but are attached in gill chambers where a constant supply 

 of food is assured. Special attaching organs, arising from specially 

 modified cilia, are characteristic of holotrichous and of some peri- 

 trichous forms. These are best developed in Trichodina (common 

 on Hydra) where a special attaching organ termed the scopula is 

 characteristic, while the two arms of EUohiophriia mentioned above, 

 are interpreted by Chatton as representing a split scopula. Amongst 

 the Holotrichida, ectoparasitism is characteristic of the group 

 which Chatton calls the Thigmotricha (1923). Here a portion of 

 the posterior ciliated region termed the "thigmotactic area," 

 becomes modified as an attaching organ. It is an adhesive knob 

 in Ancistnim, and a protrusil)le tentacle in Ilypocomides and 

 Hypocoma which Chatton, perhaps correctly, removes from the 

 Suctoria to the Holotrichida. It is rudimentary in Plagiospira and 

 not at all evident in Boveria. Two types of feeding adaptations 

 are evident in these forms. In one series the peristome and adoral 

 zone become greatly enlarged forming a helicoid spiral in Boveria, 

 Placjiospira, Heviispira and Ancistrum, capable of drawing in food 

 particles from a distance. In another series the oral apparatus 

 becomes rudimentary or lost altogether, food substances being 

 absorbed by osmosis through the general body wall or b\' tentacles 

 only as in Hypocoma and Hypocomides. 



