612 
OCEANOGRAPHY: J. F. McCLENDON 
There is then every indication that further study will show that the 
colors of crabs and their capacity to change them vary from species to 
species according to the same general rules that appear to prevail 
among fishe-s.^ But if in two groups of animals so widely separated the 
same laws of coloration prevail, and if the observed facts point so unani- 
mously to the concealing function of coloration in each, it becomes in- 
creasingly improbable that other laws prevail as extensively as has 
been supposed among other animals, and increasingly evident that 
adaptation of the organism to its environment is one of the most striking 
of natural phenomena. 
1 Darwin, C, Descent of Man, Chap. 9. 
«Cowles, R. P., Washington, Carnegie Inst., Pub., No. 103, 1908, (1-41). 
sLongley, W. H., /. Exp. Zool., Wistar Inst. Philadelphia, 23, 1917, (536-601). 
THE EQUILIBRIUM OF TORTUGAS SEA WATER WITH CALCITE 
AND ARAGONITE 
By J. F. McClendon 
DEPARTMENT OF PHYSIOLOGY. UNIVERSITY OF MINNESOTA, AND TORTUGAS LABORATORY. 
CARNEGIE INSTITUTION OF WASHINGTON 
Communicated by A. G. Mayer, August 30, 1917 
The question of the solubility of calcite and aragonite in sea water 
is a matter of interest in relation to the geology of limestone and dolo- 
mite. Murray and Hjort^ maintain that sea water is so complicated a 
mixture that the solubihty of CaCOs cannot be calculated with cer- 
tainty (from the law of mass action) but that the experiments of Ander- 
son and of Cohen and Rahen show that sea water is saturated with 
calcite. They add, (p. 181) that dolomite is less soluble than calcite in 
carbonated waters. Their book summarizes observations showing that 
calcium carbonate is precipitated in shallow tropical waters, but that 
even shells are dissolved in the red clay bottoms of the depths. 
Mayer^ placed pieces of Cassis shell in sea water for more than a year 
and found them to maintain their weight within about tV of 1%. The 
precipitation of CaCOs at Tortugas was studied by T. Wayland Vaughan, 
R. B . Dole, and G. H. Drew.^ Drew observed that a denitrifying bacillus, 
Pseudomonas calcis, obtained from the sea water, was capable of changing 
calcium nitrate to calcium carbonate in culture media and supposes a 
similar process to occur in sea water. Since Vaughan has observed 
that calcium carbonate is constantly precipitating at Tortugas, Drew's 
hypothesis necessitates the presence of an appreciable amount of nitrates 
or nitrites, and I have attempted to determine them. 
