biology such as the structure of the larvae and development of the egg provide strong evidence that echinoderms may be closely related to the group which gave rise to the vertebrates. The eggs of sea urchins have been used as subjects for fundamental research on cell structure, fertilization and experimental embryology (16,17). In recent years sea-urchin eggs have even been shot into space in rockets to find out whether cosmic rays or other such phenomena have an effect on living organisms. Their relatively short development period allows researchers to observe the teratological effects of drugs, since adverse reactions can be noted in a matter of days instead of weeks or months (7), and there is potential for the use of sea urchin larvae in bioassay techniques (1). Interest has been shown recently in the large spines of the Slate-pencil Urchin, Heterocentrotus mammillatus since the structure of the material of which they are composed may provide a template for the synthesis of artificial bone (13). Several echinoderms have been found to contain active compounds that may be of use medicinally. Holothurin, a steroid saponin isolated from the Bahamian sea cucumber Actinopyga agassizi suppresses the growth of tumours in mice, and holothurin-like substances from other sea cucumbers and sea stars elicit a variety of effects on a number of biological systems. Crude extracts of the sea stars Asterias forbesi Acanthaster planci and Asterina pectinifera are effective against influenza B virus in embryonated chicks, and the sea cucumber Stichopus japonicus is the source of two extracts, one of which shows antitumour activity, the other exhibiting high antifungal activity (20). Echinoderms have been used for food since before the time of Aristotle (16). Currently 50 000 tonnes of echinoderms are harvested annually, most of which are sea urchins, although in the South Pacific holothurians have a greater relative importance (19). Sea urchins of various species are marketed in a number of countries, largely as a luxury food. Paracentrotus lividus is collected in Ireland, the Mediterranean and Brittany (see data sheet), Tripneustes ventricosus in Barbados and Loxochinus albus in Chile (9,12). Strongylocentrotus franciscanus is collected on the west coasts of the U.S.A. and Canada and S. droebachiensis on the east coasts. The gonads are sold fresh or frozen, and are particularly popular with Italians and other immigrants (16). In Japan S. intermedius Heliocidaris and Hemicentrotus are fished commercially, the former being the most important. In Australia surveys are in progress and a fishery for Heliocidaris erythrogramma Tripneustes sp, Centrostephanus and Phyllacanthus is being considered (31). Dried sea cucumbers, known as trepang or beche-de-mer, were among the earliest products of the South Pacific to enter international commerce. In the Far East they are highly regarded as an aphrodisiac, a tonic and as a cure for various illnesses, particularly high blood pressure. However, their most important use is as a food, their protein content being as high as 3 per cent. The main consumers are the Chinese, both in China and in countries throughout South East Asia. Hong Kong and Singapore (the main trading countries) both import more than 'f50 000 kg annually; imports into Japan, Taiwan, the U.S.A. and France have increased recently and Australia also has a small market. The trade has always been run on a cottage-industry scale, and local processing on coral cays and in coastal towns has been found to be more economically feasible than large central processing factories. Sources of supply are scattered from the east coast of Africa to the South Pacific, the main exporters being Fiji, the Solomon Islands, Papua New Guinea, Palau, Sri Lanka, Indonesia and the Philippines. Only a few species are commercially valuable, the most important being Microthele nobilis and Actinopyga miliaris and the best quality coming from the South Pacific. Sea cucumbers are easy to catch; in the Solomon Islands, over a period of nine days, 7122 specimens of H. nobilis were caught by local fishermen, an average of 11 specimens per man per hour (19,25,27,28,29,30). In the U.K. sea urchins are collected for the curio trade (see Echinus esculentus data sheet), and dried starfish and sand dollars are collected in other parts of the world for ornamental purposes. 540