Cartoon of a T. brucei cell, emphasizing the evolutionarily-conserved character of the 9 + 2 flagellar axoneme, with various ciliated organisms representing the radial spokes that extend inward from the outer doublet microtubules toward the central pair. The paraflagellar rod, unique to trypanosomes, is not shown. Drawing design by Desiree Baron and Zachary Matheny. Adapted from Ralston et al. 2009, with permission.