378 



GRACE MEDES 



48 hours and c after 72. By the 96 hour period, all are smaller 

 than those in the control. 



Frary and Nietz ('15) give a table of the hydrolysis of so- 

 dium carbonate in solutions at 25°C., according to which 

 0.005M Na2C03 furnishes concentration of hydroxyl ions equiva- 

 lent to a 0.00081M NaOH solution. By interpolating in the 

 table, the addition of 0.8 cc. 0.45M NaaCOs (lie) to 100 cc. 

 water w^ould furnish approximately the same concentration of 

 hydroxyl ions as addition of 0.66 cc. M/10 NaOH (66). These, 

 being in distilled water, would not have the same values as 

 when added to sea-water, but it seems significant that in the 



Plot 12 



two experiments, these two solutions produce strikingly similar 

 modifications of the growth-curves. 



The modifications found in the Na2C03 solutions were of very 

 much the same type as in those of the NaHCOs, except that 

 the changes were not apparent so early. In these solutions the 

 lattice-formation was very evident, even more so than in the 

 control cultures, and persisted until a later stage. Figures 

 88, 89 and 90 represent specimens from a, c and d at 48 hours; 

 figures 91 and 92, specimens from solution e; figures 93 and 

 94, two from solutions /; figure 95, one from g. In comparison 

 with those of the same age in Experiment 9, it may be seen 

 that the skeleton is heavier and the lattice-formation persists 

 later. For instance, the specimens represented in figure 91 



