ZOOFLAGELLATES 137 



Because of their importance as blood parasites of mammals, 

 including man, the trypanosomatid flagellates have been subjects 

 of a wide range of studies. The group includes internal symbiotes, 

 pathogenic or not, of vertebrates, invertebrates, and plants ; and 

 a life cycle involving alternating insect and other animal or plant 

 hosts is common. Different life cycle stages and different genera 

 vary in body shape and size and in the location relative to the 

 nucleus of the kinetosome and of an organelle known as the 

 kinetoplast or kinetonucleus (see Grasse, 1952, or any textbook 

 of protozoology or parasitology for characterization of genera 

 and life cycles). They may be considered together here since our 

 information for the most part concerns morphological features 

 common to all of them. 



Structure of the flagellum and pellicle in whole dried cells was 

 reported by Kleinschmidt and Kinder (1950), Lofgren (1950), 

 Das Gupta, Battacharya, and Sen Gupta (1951), Kraneveld, 

 Houwink, and Keidel (1951), Das Gupta, Guha, and De (1954), 

 Meyer and Porter (1954), Ray, Das Gupta, De, and Guha (1955), 

 and Inoki, Nakanishi, Nakabayashi, and Ohno (1957). Sectioned 

 material has been studied by the Inoki group (pp. cit. and 1958), 

 Anderson, Saxe, and Beams (1956), Chang (1956), Newton and 

 Home (1957), Home and Newton (1958), Meyer, Oliveira 

 Musacchio, and Andrade Mendonca (1958), Pyne (1958, 1960a), 

 Pyne and Chakraborty (1958), Chakraborty and Das Gupta (1960), 

 Clark and Wallace (1960), Meyer and Queiroga (I960), Newton 

 (1960), Steinert (1960), and Steinert and Novikoff (1960). 



In all species seen, the pellicle is conspicuously fibrillar (Fig. 53, 

 PL XIV). Whole mounts show that the fibrils spiral about the 

 body of the cell and converge, with reduction in number by 

 fusion, at the two poles. In sections, the fibers are seen to be 

 tubular, probably about 25 m/z in diameter (lower figures seem 

 to represent measurements of one wall of an obliquely-cut fibril). 

 They are evenly spaced in a single layer just below the continuous, 

 three-ply, limiting membrane. 



The flagellum has the usual 11 fibrils in a somewhat inflated 

 sheath. In most published micrographs, a rod of dense material 

 is evident lying close alongside the fibril bundle. In forms with 

 an undulating membrane, the expanded flagellar membrane 

 adheres firmly along one side to the body surface; the nature of 



