EDWIN J. COHN. 



Such concentrations of spermatozoa as were used in the experi- 

 ments reported in the last section probably never occur in the 

 ocean. The conditions that obtained in these experiments 

 approximate those of ripe sperm in the testes very much more 

 closely than they do those of sperm that are shed into the ocean. 

 The hydrogen ion concentration in these suspensions increased 

 not inconsiderably as a result of carbon dioxide produced by the 

 sperm. This rise in carbon dioxide (and also in hydrogen ion) 

 concentration was measured. The hydrogen ion and carbon 

 dioxide concentration of the suspensions in which spermatozoa 

 lived for the longest time was sufficiently great to inactivate 

 spermatozoa. The length of life of concentrated sperm suspen- 

 sions is therefore for the most part ascribable to the hydrogen ion 

 concentration of such suspensions. 



The length of life of a sperm suspension at different hydrogen 

 ion concentrations was determined. 



Two criteria of the length of life of the sperm were employed. 

 The fertilization tests are reported. The hydrogen potential of 

 the sea water was determined by colorimetric comparison with 

 standardized mixtures of borates or phosphates in the way that 

 that has already been described (p. -171). 



In the experiments to be reported the hydrogen ion concentra- 

 tion was decreased by the addition of sodium hydroxide to sea 

 water. The hydrogen ion concentration was increased by the 

 addition of hydrochloric acid. 



When an acid stronger than carbonic acid is added to sea water, 

 carbonic acid is displaced from its salts and carbon dioxide is set 

 free. As the carbon dioxide that is set free diffuses from the 

 solution the hydrogen ion concentration decreases, until the 

 carbon dioxide of the sea water is again in equilibrium with the 

 partial pressure of that gas in the air. The hydrogen ion con- 

 centration that is eventually reached is different from the original 

 hydrogen ion concentration of the sea water, but nearer to it 

 than to the hydrogen ion concentration immediately after the 

 acid is added. This regulation of the neutrality persists until all 

 of the carbonates have been decomposed. The rate at which 

 equilibrium is approached depends upon the temperature, the 

 surface, and the degree of agitation. 



