Fig. 4. Bristles lacking fascin crossbridges still form microvilli. (a,b) Transverse sections of newly emerged bristle tip from 34-hour-old singed^X2 mutant pupa. A smaller version appeared in Tilney et al., (1998) and is included here at sufficient magnification in panel b so that the aggregated core bundles (arrows) of the microvilli can be clearly visualized. Panel b, published with permission by Rockefeller University Press. The size of these bundles and the number of filaments per bundle are similar to those in microvilli at the bristle tip (e.g. Fig. 2e) or to those in longitudinal section (panel d). (c,d) Grazing longitudinal section through a singed^X2 bristle tip at the same magnification as in panels a and b, respectively. The bundles are indicated by arrows. Note that the diameters of the bundles here are the same as in panel b and in Fig. 2e.