1. Wilkinson, P. C., Nature, 244, 512–513 (1973).
2. Wilkinson, P. C., Nature, 251, 58–60 (1974).
3. Wilkinson, P. C., in Primitive Sensory and Communication Systems: the Taxes and Tropisms of Microorganisms and Cells (edit. by Carlile, M. J.) (Academic, New York, in the press).
4. Bernheimer, A. W., in Microbial Toxins (edit. by Ajl, S. J., and Montie, T. C.), 184–212 (Academic, New York, 1970).
5. Doery, H. M., Magnusson, B. J., Gulaskharan, J., and Pearson, J. E., J. gen. Microbiol, 40, 283–296 (1965).