Cytoplasm of a green Trichodina that lives on the surface of a freshwater snail collected in central Illinois. In this view the abundant endosymbiotic zoochlorellae and a single endosymbiotic bacterium are evident. The bacterial endosymbiont is filled with virion particles. In related images the particles can also be seen loose in the cytoplasm of Trichodina. See the serial section CIL:25687). TEM taken by G. Antipa in 1968 on a Hitachi HU11A operating at 75kV. The negative magnification is 11,500X. 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 65nm thickness.