160 ELECTRON-MICROSCOPIC STRUCTURE OF PROTOZOA 



closed within the flagellar membrane occur in Peranema, in the 

 localized paraflagellar body of Eugkna, in the flagella of trypano- 

 somes and bodonids, in the recurrent flagellum of some tri- 

 chomonads, and in the adherent flagella of Pyrsonympha. Except 

 for the paraflagellar body, these are lengthy rods or bands of 

 dense or fibrous material. Their distribution suggests that they 

 may function as stiffening or supporting structures, as proposed 

 above for Pyrsonympha. They usually appear in flagella that 

 adhere to the cell body, but are present in some free flagella 

 as well. Critical studies of flagellar movement or sensitivity in 

 series of species with variously modified and with simple flagella 

 have not been attempted but certainly are needed. 



Very little can be said about observed differences in the narrow 

 region at the base of the flagellum where the central fibrils arise 

 and where the cell membrane establishes its relationship with the 

 flagellum. This must be in all flagella a particularly critical region 

 both physiologically and developmentally ; the more detailed our 

 observations of its ultrastructure and variations, the more abysmal 

 seems our ignorance of what actually goes on here. We face a 

 similar lack of food for speculation as regards the structures seen 

 occupying the center of the kinetosome in several species, as well 

 as the fine fibrillar interconnections among kinetosomal fibrils 

 and subfibrils illustrated by Gibbons and Grimstone. Their 

 finding of elaborately different kinetosomal contents within the 

 same species indicates that the matter must be of considerable 

 importance to the kinetosome, but we cannot begin to guess 

 why or how. 



At least two fairly distinct types of fibrils arising from kineto- 

 somes or centrioles have been widely observed. The first of these 

 includes the striated rhizoplasts and other striated root fibrils 

 of some chrysomonads and phytomonads, the striated parabasal 

 fibrils of trichomonads, Foazna, and Trichonympha, the costa of 

 trichomonads, and the striated axial ribbons of Pyrsonympha and 

 Joenia. They vary widely in diameter; their repeating pattern is 

 from 30 to 60 m/x in length. In addition to their periodic structure 

 and kinetosomal origin, they have other features that recur 

 repeatedly. Intimate association of their distal regions with the 

 nucleus is seen in several phytoflagellates and again in Pyrsonympha, 

 while it is known that in many trichonymphids the parabasal 



