ABSTRACT
The close proximity of the mantle to the shell begs the inference that it is the primary tissue of shell formation. Virtually all of the literature on the metabolism of ions by mantle is confined to studies of the inner region dorsal to the pallial line. In short-circuit experiments, isolated shell-facing mantle layers from freshwater bivalves have the equivalent of a positive current toward the shell. The promulgation of the idea that matrix is more than a structural component and may actually regulate the formation of the diverse crystal microstructures has led to an expanding interest in understanding the interaction of matrix components with forming mineral. Molluscs are favorable systems for studying CaC03 deposition because of the arrangement of the shell-forming tissue, the mantle, as a discrete sheet of tissue lying next to the shell, and, in so doing, describing, at least theoretically, a set of well-defined compartments.
