The use of secondary electron (SE) signals in the scanning electron microscope provides a wealth of information on the cortical topography of the ciliated protozoa. Surface manifestations of such morphogenetic events as cell division and regeneration can easily be visualized in the SE mode of the SEM, but concomitant alterations occurring below the surface of the cell can not be visualized. Ciliatologists have used the "Protargol" (silver protein) method to study the cortical features of the ciliates at the light microscopical level. The protein silver stain clearly reveals cilia, microtubules, kinetosomes and nuclei. Small et al. have demonstrated the usefulness of this technique in conjunction with backscatter electron (BSE) detection in the SEM. A strong BSE signal can be obtained from argentophilic structures within the specimen due to the atomic number contrast between the deposited silver and the low atomic number elements normally found in cell cytoplasm. Therefore, the use of the SE and BSE signals with good spatial resolution should clearly demonstrate the relationship between surface and subsurface features.