The siphuncle, which is believed to empty the newly formed
chambers of the shell by a process involving the active transport of NaCl, has the
metabolic, enzymatic, and morphological features of a transporting epithelium.
It is capable of removing monovalent ions from solutions containing only Na+
and no Cl- or divalent ions, or only Cl- and no Na+ or divalent ions, indicating
no obligatory coupling. The Na+ and Cl- are removed from native cameral fluid
at approximately the same ratio. The levels of K + and the divalent ions are also
lowered, but at slightly different rates. Neither H+ nor NH1 accumulate in
cameral fluid to an appreciable extent
