i8o 



EDWIN J. COHX. 



no such accuracy can be attained as in the measurement of the 

 hydrogen potential of sea water, since the cloudiness of the more 

 concentrated suspensions makes the colorimetric determination 

 difficult and since the intensity of the indicators changes more 

 rapidly in the presence of sperm. This is probably due to the 



ION Co/vce/vrAr/ow 



O 4. o.oy<K. 



Jr. 0.02. * 



Q 6. O.OI % 



7 O-OOS* 



HOURS 



DIAGRAM I. 



penetration of the indicators into the cells and observations sug- 

 gest that this depends upon the physiological condition of the 

 sperm. These effects can, however, be prevented from inter- 

 fering with the measurement of the hydrogen potential of the 

 suspensions if the measurements are made immediately after 

 the indicators are added. If these precautions are observed, a 

 sufficient accuracy for biological purposes can be attained. 



The data obtained in this way are in Table II. and are graphi- 

 cally represented in Diagram I. The ordinate represents the 

 hydrogen potential of the suspensions; the abscissa, the time in 

 hours. The concentration of sperm in each suspension is re- 

 corded in the accompanying tabulation. Since the increase in 

 hydrogen ion concentration is due to the carbon dioxide produced 



