STUDIES IN THE PHYSIOLOGY OF SPERMATOZOA. 213 



activity and increases the length of life of spermatozoa. Lower 

 temperatures or greater acidities destroy spermatozoa, and the 

 more so the longer they are subjected to these abnormal media. 

 Conversely, within limits, decreasing the hydrogen ion con- 

 centration or increasing the temperature increases the activity 

 and decreases the length of life of spermatozoa. Further in- 

 crease in temperature or in alkalinity irreversibly agglutinates 

 spermatozoa. 



4. The ability of spermatozoa to fertilize eggs of the same 

 species is a function of their activity (as measured by their carbon 

 dioxide production, or its converse, their length of life). Sper- 

 matozoa lose their power to fertilize as a function of the time of 

 insemination, and of the dilution and of the hydrogen ion con- 

 centration of the suspension. If spermatozoa that have been 

 in the suspension for but a short time are added to eggs in a large 

 volume of sea water a decrease in the hydrogen ion concentration 

 of the sperm suspension (that is, an increase in the alkalinity) 

 increases the activity and the fertilizing power of the sperma- 

 tozoa. Such spermatozoa will, however, lose their power to 

 fertilize when transferred to ripe eggs in sea water long before 

 spermatozoa that have been relatively inactive in more acid 

 sperm suspensions. 



5. If spermatozoa that have been at the same hydrogen ion 

 concentration are added to eggs in sea water at the same time, 

 increasing the concentration of spermatozoa increases the per- 

 centage of eggs that are fertilized. This may be explained either 

 by assuming that in the greater concentration more spermatozoa 

 will on the average arrive at the periphery of the egg with suffi- 

 cient action (having the dimensions of energy X time) to initiate 

 development, or by assuming that mass action of spermatozoa 

 may be effective in initiating the development of the sea urchin 

 egg. The latter explanation has been suggested by Glaser, who 

 pointed out that the further assumption that more than one 

 spermatozoon was necessary "to carry out the bi-parental effect'' 

 was not involved. 



6. Increasing the carbon dioxide concentration increases the 

 hydrogen ion concentration of the suspension, decreases the 

 activity of spermatozoa and increases the length of their life. 



