Dissected midgets were fixed in 2.5% glutaraldehyde+2% formaldehyde in 0.1 M PIPES buffer (pH 7.4) for 1 hr at room temperature, washed in buffer, post-fixed in 1% osmium tetroxide in buffer for 1 hr, washed in deionized water, and stained with 2% aqueous uranyl acetate for 30 mins. Specimens were dehydrated through an ethyl alcohol series, infiltrated with Spurr's resin and flat embedded at 60uC. Longitudinal sections (50 nm) were cut on a Leica UC2T ultramicrotome onto uncoated 150 mesh copper grids, counter-stained with lead citrate, and viewed in an FEI CM12S electron microscope operated at 80 kV. TIFF mages (8 bit) were collected via an AMT 4 M pixel camera and used for image analysis.