1. A.M. Roberts, Geotaxis in Motile Organisms, J. Exp. Biol. 53, 687 (1970).
2. Also A.M. Roberts, Hydrodynamics of Protozoan Swimming, in Biochemistry and Physiology of Protozoa, Vol. 4, 2nd Ed., M. Levandowsky and S. Hutner, eds., Academic Press, New York, 1981, pp. 5–66.
3. A similar development is given in A.M. Roberts, the Biassed Random Walk and the Analysis of Microorganism Movement, in Swimming and Flying in Nature, Wu, Brokaw and Brennen, eds., Plenum, New York, 1975, pp. 377–393. A rudimentary version of the theory is given by Lord Rothschild, in Spermatozoan Motility, D.W. Bishop, ed., Am. Assoc. Adv. Sci., Washington, D.C., 1962, pp. 13–29.
4. “Rheotaxis”, described by Roberts [3], is one component of gyrotaxis.
5. S. Childress, Mechanics of Swimming and Flying, Cambridge University Press, Cambridge, 1981, provides a list of references.