358 GRACE MEDES 



A = 1.84, his maximum value, obtained from water of the Basin 

 of the United States Fisheries Laboratory. Garrey gives his 

 average freezing point depression at Woods Hole at a = 1.81, 

 which he says is equivalent to a specific gravity of 1.02426. His 

 variation in concentration, then from a = 1.78 to a = 1.85 

 would range from 1.02385 to 1.02479 at 31.5°C. Taking 1.02426 

 therefore as the normal concentration of the sea-water in that 

 region, we would obtain a range of variation of about 5 per 

 cent in Arbacia larvae between these two extremes. 



The second series of experiments dealt with the effects of 

 acidity and alkalinity, and for this purpose the following solutions 

 were employed: 



Experiment 4, 5 Sea-water + CH3COOH 



Experiment 6, 7, 13 Sea-water + NaOH 



Experiment 8,9,10 Sea-water + NaHCOs 



Experiment 11, 12 Sea-water + Na2C03 



The Na2C03, being technically a salt, grades over into the 

 next series of experiments, but its alkaline reaction, due to 

 the fact that it is the salt of a strong base with a weak acid, 

 relates it more closely in its physiological effects to the other 

 experiments of this series. 



Two experiments were performed with the acid solutions. 

 The first was begun September 8, 1914. This was the last 

 experiment of that season, and mature females were exceed- 

 ingly difficult to obtain. Moreover, the death-rate, even in 

 the control cultures, was so high that the eggs did not lend 

 themselves well to experimental conditions. The data obtained 

 are given, however, as a basis for comparison with similar 

 experiments under more favorable circumstances. 



The solutions employed were: 



Experiment 4. Plot 7. September 8, 1914 



a Sea-water 



b '. 99.75 cc. S. W. + 0.25 cc. N/10 Acetic acid 



c 99.50 cc. S. W. + 0.50 cc. N/10 Acetic acid 



d 99.25 cc. S. W. + 0.75 cc. N/10 Acetic acid 



e 99.0 cc. S. W. + 1.0 cc. N/10 Acetic acid 



