Fig. 2. (A) The positions of microtubules in transverse sections of axonemes from T. brucei. Points show the positions of the centres of either the CP microtubules or the A-tubules of the outer doublets. Dotted lines show the x' and y' axes of the axoneme (see Materials and Methods) and also a regular normal nonagon. The number, N, indicates the number of independent micrographs combined in the diagram. (B) Radial distribution of the doublets and the CP microtubules in transverse sections of axonemes from the wild-type trypanosomes. Since the CP are indistinguishable on the electron micrographs, their distribution can be anywhere in the range 0-180°, whereas the distribution of the doublets is 0-360°.