[…]the trams floating slowly down Swanston Street, paper-sellers cutting open bundles with Stanley knives, the smell of ground coffee from the downstairs cafe,[…].

a lapidary mill

Calcium ions are present in this fluid. The millipores within the enamel contain this electrolyte , separated by the positive and negative poles; the cathode is the outer enamel, and the anode is the internal enamel.

Note how the zygophores are tightly appressed parallel to each other while fusing to form the progametangia.