High resolution image of the cross section through a radial arm of the contractile vacuole complex. The collecting canal occupies the center of the arm whose membrane is supported by the radial microtubular ribbon which has now divided into at least six segments and surrounds the canal. Gaps between the segments are where the mass of membrane tubules of the smooth spongiome opens into the canal. Decorated tubules occurring in bundles form the peripheral layer of the radial arm. TEM taken on 5/2/79 by R. Allen with Hitachi HU11A operating at 75kV. Neg. 18,000X. The raw film was scanned with an Epson Perfection V750 Pro. This image is best used for quantitative analysis. Standard glutaraldehyde fixation followed by osmium tetroxide, dehydrated in alcohol and embedded in an epoxy resin. Microtome sections prepared at approximately 75nm thickness. Additional information available at (http://www5.pbrc.hawaii.edu/allen/).