a1 The Laboratory, Marine Biological Association, Citadel Hill, Plymouth
This is the second of three papers describing the structure, properties and buoyancy function of the spermaceti organ of the sperm whale (Physeter macrocephalus Linnaeus 1758). The first paper (Clarke, 1978a) described the detailed structure and proportions of the spermaceti organ and related structures and considered relevant details of the blubber, skin and lungs. Here, three thermal properties of the spermaceti oil are described which are relevant to a study of the function of the oil. Finally, in a third paper (Clarke, 1978b) it will be shown that, over its great geographical and depth ranges, the whale varies considerably in buoyancy due to variations in water density and the volume of air in its lungs and it is suggested that, during dives, the whale can control its own density by changing the temperature of the spermaceti oil of the head and may attain neutral buoyancy in dives deeper than 200 m.