Study of the pH relations of the coralline algae has shown that there is good reason to believe that calcification may be brought about by the development of alkalinity by the cells of the thallus, while a slightly acid reaction may be detected on occasion on the outer surface (Digby, 1977). The mechanism of calcification is obscure, but in general two types of action might be involved, direct chemical action and active transport. In direct chemical action a chain of reactions may occur in which the laws of chemical equivalence must be obeyed. Active transport involves complex metabolic processes which may be much more efficient in moving ions from one place to another, the utilization of one chemical equivalent of oxygen providing the energy to transport more than one equivalent of a particular substance.