28 STRUCTURE 



Fibrils of the same size and appearance are found in various parts 

 of many cells, and particularly in protozoa. Secondly, fine fibrils 

 may be found connecting the basal bodies of the component cilia 

 of compound structures like cirri and membranelles (see PL Va) 

 Similar fine connexions (about 20 A in diameter) have been found 

 between adjacent basal bodies of Trichonympha flagella (Fig. 17, 

 p. 72). 



The third type of root takes the form of striated fibres. The 

 diameter of these fibres varies between wide limits and the 

 striation period usually lies between 300 and 700 A, with or 

 without intraperiod bandings. In fact, several of the best resolved 

 micrographs of fibres show a period of 650 to 700 A with several 

 intraperiod bands (see PL XIV) (Fawcett, 1958b; Gray, 1960; 

 Anderson and Beams, 1959), comparable with the 550 A periodi- 

 city of discharged trichocysts of Paramecium (Sedar and Porter, 

 1955) and the 640 A periodicity of collagen fibres, although 

 collagen is normally found extracellularly and has a somewhat 

 different intraperiod banding pattern. Several workers have found 

 the striated fibres to be made up of many longitudinal filaments; 

 these were 50 A in diameter in the rotifer Philodina (Lansing and 

 Lamy, 1961a) and 45 A in diameter in Anodonta (Gibbons, 1961b) 

 (PL XI Vc). Striated fibres may connect or form bundles with 

 those from other cilia as do the striated kinetodesmata of some 

 ciliated protozoa, or may run deep into the cytoplasm of the cell 

 without any obvious connexion as do the roots of the cilia of the 

 locust scolopale organ (Gray, 1960) and some cilia of molluscs and 

 other metazoa (Fawcett, 1958b). 



Chemical Nature 



We are sadly ignorant about the chemical nature of the parts of 

 cilia and flagella. The recent work of Tibbs (1957) on flagella of 

 the alga Polytoma and on fish sperm tails, and of Child (1958, 1959) 

 and Watson, Hopkins and Randall (1961) on cilia of the protozoon 

 Tetrahymena have confirmed some previous suggestions and also 

 brought out some new facts. The first problem is to isolate the 

 ciliary organelles and make certain how much has been lost in the 

 preparation. Child found by electron microscopy that his isolated 

 cilia were bundles of fibrils, but could not be certain how many 

 fibrils were present in the bundle, or if the membrane was present; 



