About ten years ago, one of the authors participated in a review of haemocyanin structure and function (van Holde & van Bruggen, 1971). At that time, it was possible to describe the field in terms of a limited amount of exciting new structural information, and a long list of unanswered questions. While the stoichiometry of oxygen binding was understood, virtually nothing was known about the active site. Even the oxidation state of the copper was a matter of conjecture. The size of the haemocyanin polypeptide chains was the subject of intense debate, with very little substantive knowledge available. While the haemocyanins were known to be allosteric proteins, there were virtually no experimental studies of oxygen binding on a level that could be meaningfully interpreted in terms of extant theories.

Information on the swimming motion of microscopic calls and the factors which affect it is important to a wide range of disciplines. The functions of the motile apparatus of simpler organisms such as bacteria or algae can provide useful clues on the operation of more complex contractile systems such as muscles. Often celluar motility is a response to conditions external to the cell (e.g. chemotaxis) and, hence, can lead to increased understanding of the cell's sensory capability. On the medical front there is a physical similarity between the flagellar beat of the motile spermatozoa and the ciliary activity of epithelial lining of respiratory and reproductive tracts. Impairment of the motile apparatus can lead to sterility and to a variety of pathological conditions. In animal husbandry, in the artificial insemination industry and in sperm banking estimates of the extent of cellular motility and the fraction of cells which are motile are key quantities which can determmine the fertilization capability of a semen sample.