372 



GEACE MEDES 



there was a gradual shifting toward the bottom, of the growth- 

 curves of those in higher concentrations of the hydroxyl, with 

 the specimens of the control ultimately the largest. 



The growth-curves of / and g reach their maxima 24 hours 

 later than the others. In solutions of less alkalinity, skeletal 

 resorption was more rapid and at the close of 120 hours the 

 positions of all the cultures were the reverse of that indicated 

 at the age of 72 hours. 



Another experiment was made with NaHCOs added in greater 

 proportions in order to determine the effects of still higher 

 concentrations of the acid salt. For this purpose the following 

 solutions were employed: 



Experiment 9. Plot 11. July 15, 1915 



a Sea-water 



h 98.5 cc. S. W. + 1.5 cc. 0.45M NaHCOa 



c 97.0 cc. S. W. + 3.0 cc. 0.45M NaHCOs 



d 95.5cc. S. W. + 4.5 cc. 0.45M NaHCOs 



e 94.0 cc. S. W. + 6.0 cc. 0.45M NaHCO? 



/ 92.5 cc. S. W. + 7.5.CC. 0.45M NaHCOs 



g 91.0 CC. S. W. + 9.0 CC. 0.45M NaHCOs 



The corresponding measurements were: 



cc 

 b. 

 c. 

 d 

 e. 

 f- 



g 



24 HOURS 



28.84 

 34.15 

 30.21 

 25.94 

 21.30 

 12.11 

 2.07 



48 HOURS 



74.05 

 76.09 

 68.91 

 62.87 

 57.89 

 50.24 

 41.32 



72 HOURS 



85.91 

 86.12 

 78.18 

 70.25 

 04.19 

 56.13 

 45.77 



96 HOURS 



92.13 

 90.81 

 82.14 

 72.94 

 65.97 

 57.89 

 47.15 



120 HOURS 



95.08 

 92.74 

 83.69 

 73.98 

 66.15 

 58.02 



In this experiment also, there was shown the specific effect 

 of alkalinity upon length of skeleton. Solution b, which was 

 approximately equivalent to Se, produced a similar modifica- 

 tion of the rate of growth. In all the others, the concentra- 

 tions of the hydroxyl were greater than in any of Experiment 

 8; c, however, caused an acceleration during the first day; in 



