Observations on the metabolism of the corallines.

Abstract

The results of this investigation suggest a clearer view of the problem of lime deposits and the conditions of organic deposition. The coralline studies are widely distributed and convenient for experiment because of their activity. Although no direct record of their internal changes can be suitably followed, we can determine the changes in the external milieu—changes which will complement those occurring within the organism. In the external milieu, sea water, the carbonic acid-carbonate system, especially with Ca and Mg, is of particular biological significance.

No observations have yet been so distributed as to give complete or even consistent ideas on the whole process of carbonate deposition. Deposition may occur (1) by the accumulation of carbonates incorporated inside of organisms, or (2) by precipitation from the surrounding water by the photosynthetic removal of CO₂. Removal of single ions from sea water is impossible, and deposits within the tissues appear principally as CaCO₃. Diffusion of lime into the alga would be facilitated (1) by its precipitation within the organism and (2) by the use of carbonic acid in photosynthesis. Each process would reduce the concentration of these ions within the plant. Diffusion must essentially be, at some point, a factor limiting this process of metabolism.

Titration of sea water to an end point of pH 4.0 with methyl orange gives the excess base, or concentration of weak acid anions, called X-base.