218 



ORDER TRYPANOSOMATA. 



spores commonly follows upon the simple encystment of a single animalcule. The 

 recognition of these important reproductive phenomena is chiefly due to the recent 

 painstaking investigations of Messrs. Dallinger and Drysdale, whose researches in 

 this direction are fully recorded in the descriptive accounts given of Monas 

 Dallingerii, Cercomonas typica, Tetramitus rostrata, Dallingeria Drysdali, and several 

 species of Heteromtta. 



With reference to the variously modified characters of the oral system, and of the 

 locomotive and supplementary appendages, the class of the Flagellata may be con- 

 veniently subdivided into primary sections or Orders as below : 



A. 



Ingestive area diffuse. 



B. 



Ingestive area discoidal, 

 limited to the anterior 

 region ; no true mouth. 



C. 



Ingestive area 



constituting a true and 



distinct mouth. 



Flagellum rudimentary, sup- 

 plemented by an undu- 

 lating membrane .. .. 



Flagellum supplemented byl 

 lobate pseudopodia . . . . / 



Flagellum supplemented by) 

 ray-like pseudopodia . . J 



Flagella representing the sole) 

 organs of locomotion . . / 



Flagellum issuing from the 

 centre of a collar-like ex- 

 tensile membrane 



Flagellum not supplemented) 

 by cilia / 



Flagellum supplemented by 

 a more or less highly de- 

 veloped ciliary system 



ORDER I. TRYPANOSOMATA. 



II. RHIZO-FLAGELLATA. 



III. RADIO-FLAGELLATA. 



IV. FLAGELLATA-PANTOSTOMATA. 



V. CHOANO-FLAGELLATA. 



VI. FLAGELLATA-EUSTOMATA. 



VII. CILIO-FLAGELLATA. 



Order I. TRYPANOSOMATA, S. K. 



Animalcules flattened or lamellate, one or more of the lateral borders 

 forming a frill-like undulating membrane by the vibrations of which 

 progress is effected ; one extremity sometimes attenuate and somewhat 

 resembling a flagellum. Oral or ingestive area undefined. 



Two species only, representing but a single genus, can be as yet referred to 

 this newly established order. So far as it can be at present determined, these two 

 endoparasitic types would seem to lie at the base of all the succeeding more typical 

 sections of the Infusoria Flagellata and Ciliata. Although no positive flagellum is 

 present, the growth of such an organ is evidently foreshadowed in the slender tag- 

 like appendage of Trypanosoma sanguinis, while, on the other hand, the undulating 

 membranous border, constituting the essential organ of locomotion, may without 

 hesitation be regarded as closely, if not absolutely, homologous with the similar 

 undulating frill-like border present in the earlier developmental phases of Sttntor, 

 Euplotes, and other higher Ciliate types, and which eventually splits up to form the 

 characteristic adoral fringe. 



GENUS I. TRYPANOSOMA, Gruby. 



F" Animalcules free-swimming, compressed ; one side produced as a thin, 

 undulating, frill-like border ; the anterior extremity sometimes produced as 

 a long tag-like or flagellate appendage. No distinct oral aperture. 



Occurring in the blood of Amphibia, and within the intestinal viscera of 

 domestic poultry. 



