Relationship of Biological Regulatory Mechanisms to Learning and Memory*

are known to be, involved. In addition to shell and skeleton building, pelleting activities and burrowing can lead to some measure of mixing of organic matter with carbonate minerals, and it has been suggested that the rapid multiplication of diatoms may lead to the precipitation of calcium carbonate from sea-water as 'whitings'11• There are probably other instances, or types of rock, in which the effective organic agent or substance is not apparent in the deposit. During recent years, American oil companies, especially, have paid considerable attention to organic geochemistry. Fundamental investigations have been undertaken•,•, because these may well contribute eventually to the more effective search for new oil fields. In Europe, too, there has been similar, yet decidedly less, activity10• Universities and research institutes have also carried out investigations in organic geochemistry, the departments involved varying from place to place. Some problems require materials from distant places, or samples that are expensive to obtain. Other investigations can be made on materials that are decidedly easier to acquire. The facilities needed for effective work depend on the problem, and range widely in cost and complexity. Scope exists for many more teams to enter this fascinating field of investigation, and it is to be hoped that in the cases of university departments detailed and fundamental work will be given preference, even though the facilities may b e more limited than in major industrial organizations.