214 EDWIN J. COHX. 



Sea water of the optimum carbon dioxide concentration for in- 

 creasing the length of life of spermatozoa is also of the optimum 

 hydrogen ion concentration. It is possible, however, that carbon 

 dioxide affects the physiological condition of spermatozoa other- 

 wise than by means of ionized hydrogen. 



7. That decreasing the oxygen concentration of sea water 

 or decreasing the oxidations of spermatozoa by adding KCN to 

 sea water increases the length of their life has been reported by 

 Drzewina and Bohn. Experiments confirming their results and 

 demonstrating that under such conditions sperm are relatively 

 inactive are reported. 



8. Spermatozoa increase the carbon dioxide and, therefore, 

 the hydrogen ion concentration of concentrated sperm suspen- 

 sions to the optimum for decreasing their own activity in a very 

 short time. In such suspensions sperm live for a very long time. 

 McClendon has recently estimated that respiration in sea water 

 that raises the carbon dioxide and the hydrogen ion to a concen- 

 tration approximately equal to that which is most effective in 

 prolonging the life of a sperm suspension, uses up all of the avail- 

 able oxygen. It is therefore suggested that high carbon dioxide 

 and hydrogen ion concentration and low oxygen concentration 

 are the environmental conditions that obtain in a concentrated 

 sperm suspension. These conditions approximate those of ripe 

 sperm in the testes very much more closely than they do those 

 of sperm that are shed in the ocean. 



9. The addition of beef broth to sea water increases the length 

 of life of the spermatozoa. Gemmill suggested that beef broth 

 furnished "artificial nutrition." It is pointed out that the addi- 

 tion of beef broth to sea water increases the hydrogen ion con- 

 centration and decreases the activity of spermatozoa. 



10. Sea water that has contained the eggs of the sea urchin, 

 Arbacia, tremendously activates spermatozoa. It may be that 

 the fertilizing power of spermatozoa that are added to eggs in 

 sea water during this period of activation is increased in much the 

 same way that the fertilizing power of spermatozoa is increased 

 for a short period of time by decreasing the hydrogen ion con- 

 centration (increasing the alkalinity) of sea water. 



Subsequent to the period of activation spermatozoa become 



