Vorticella convallaria has a contractile stalk that arises from the aboral pole of the cell. The myonemes from the body converge at this pole and pass into the stalk to form a large contractile bundle called the spasmoneme. When contracted the stalk coils into a helix. The spasmoneme is partially encased in an extension of the pellicle and a thin layer of cytosol that is enclosed with plasma membrane. An additional secreted sheath surrounds the stalk. TEM taken on 4/6/72 by R. Allen with Hitachi HU11A operating at 75kV. Neg. 7,500X. Bar = 1µm. The negative was printed to paper and the image was scanned to Photoshop. This digitized image is available for qualitative analysis. There is a high resolution version of this image in the library (CIL:39517) which is available for quantitative analysis. Additional information available at (http://www5.pbrc.hawaii.edu/allen/).