Figure 5.

Model for the interaction between membranes and crystals in the CCP layer of bivalves. (a) Sequence for the disappearance of the membrane between two cells thus leading to their complete fusion onto a single one. Recession of the membrane causes the previously separated crystalline domains to come into contact. (b) Sequence for the division of cells owing to production of new membranes. These extend along the boundaries between crystalline domains. In the central cell, two membranes initiate at the opposite ends of a domain until they meet and fuse. Note how angles of triple junctions change with the origination or disappearance of membranes. Light grey indicates contracting crystalline areas and dark grey indicates expanding crystalline areas. See also figure 3i.