I J2 EDWIN J. COHN. 



mercury that represents the partial pressure of the gas in the 

 atmosphere at a total pressure of 760 millimeters, and a tempera- 

 ture of o C. 



The change in the carbon dioxide concentration of sea water is 

 not proportional to the change in the carbon dioxide tension, for 

 increase in the carbon dioxide tension is correlated with a change 

 in the equilibrium between the normal carbonates and bicar- 

 bonates in sea water. It has been calculated (Henderson, L. J., 

 and Cohn, E. J.) that the former are converted into the latter at 

 exactly the tensions of carbon dioxide that obtain in the ocean. 

 At tensions of carbon dioxide greater than these an increase in 

 tension may, as a first approximation in determining the carbon 

 dioxide concentration, be considered as an increase in free carbonic 

 acid. A "conversion table" for determining the carbon dioxide 

 concentration (or content) of sea water has been published by 

 McClendon (1917). The measurements of the total carbon 

 dioxide concentration upon which this "conversion table" is 

 based are not reported. Exact data defining the relation be- 

 tween the hydrogen ion concentration and the carbon dioxide 

 concentration of sea water are therefore still unknown. 



II. ENVIRONMENTAL CONDITIONS THAT AFFECT THE ACTIVITY 



OF SPERMATOZOA. 



That "all the phenomena connected with the origin and death 

 of the spermatozoon seem to be in accordance with the view, 

 that its motion is essential to its function" (Newport, G., 1853, 

 p. 261) was the opinion of the early investigators of the role of the 

 sperm in fertilization. Indeed so completely was the movement 

 of the "spermatic animalcules" found to depend upon tempera- 

 ture (Spallanzani, quoted from Newport, 1851, p. 235) (Prevost 

 and Dumas, 1824) (Newport, G., 1851); osmotic pressure (Koel- 

 liker, A., 1856) and hydrogen ion concentration (Koelliker, A., 

 1 856) that the observed activity of these cells was for a time sup- 

 posed to be due to Brownian movements. 



"Es fallt somit die Theorie, die Bewegung der Samenfaden 

 sei willkiirliche thierische Bewegung, haltlos zusammen. Welche 

 physikalischen Krafte aber dieses Phanomen erzeugen mogen, 

 ist noch vdllig dunkel. Ja wir konnen noch nicht einmal mit 

 Bestimmtheit behaupten, obwohl diess wahrscheinlich ist, dass 



