Abstract

Free swimming cells of the ciliated protozoan Tetrahymena are attracted to certain chemicals by chemokinesis. However, a special type of chemotaxis in response to a chemical gradient is found in cells gliding very slowly in semisolid media. In contrast to classical chemotaxis by leukocytes, which is solely positive towards chemo‐attractants, the oriented chemokinesis by gliding Tetrahymena involves both positive and negative elements. The major chemo‐attractants are peptides and/or proteins, and they may be compounds which signal the presence of food in the natural environment of this freshwater phagotroph.