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Pub. Puget Sound, Biol. Sta. Vol. 2, No. 40 



whether it reacts with the sea-salts liberating carbon dioxide is yet to 

 be determined. In these experiments the solutions were all used fresh, 

 as it was found that the same hydrogen ion concentration gave different 

 amounts of iodine titration when freshly made up and after standing 

 for several days. 



The hydrogen ion concentration was determined by colorimeters 

 made according to the formulas of Clark and Lubs (1917), and is ex- 

 pressed in terms of the pH. The buffer solutions for these were made 

 up by Dr. E. B. Powers of Colorado College. The average sea-water 

 in Puget Sound varies in pH from 7.8 to 8.4. The approximate normality 

 and corresponding pH of the sulphurous acid used is given in table 1. 

 A correction of .15 cc. had to be made to allow for the absorption of 

 iodine by the sea-water. 



Table 1. Showing the approximate normality of H^SO^ as found by 

 titration with iodine; and the corresponding pH 



Three types of experiments were performed: (1), Testing the sensi- 

 tivity of unfertilized eggs and sperms (table 2); (2), Testing the sensi- 

 tivity of fertilized eggs to acid at different stages of their development 

 (table 3) ; (3), Testing with 4 to 6 hours exposure to the acid at different 

 stages and then developing further in sea-water (table 4). 



