STUDIES IN THE PHYSIOLOGY OF SPERMATOZOA. 1 97 



cannot affect those changes in the egg-coverings" (Glaser, O., 

 1915, p. 153) which are necessary to fertilization, has unques- 

 tioned significance. The older the spermatozoa and the more 

 their available energy has been expended, the more spermatozoa 

 are necessary in order to effect fertilization. There is, however, 

 even then no doubt that "a single spermatozoon is sufficient to 

 carry out the bi-parental effect" (Glaser, O., 1915, p. 153). 



The "fertilizing power" of sperm at the same hydrogen ion 

 concentration is, therefore, in some way dependent on the con- 

 centration of the sperm. In Experiment 228 in Table IX. (p. 196) 

 a o.ooi per cent. ; a 0.005 per cent, and a o.oi per cent, suspension 

 was made from the sperm of one male. The "fertilizing power' 

 at each hydrogen ion concentration was lost the sooner the 

 smaller the concentration of sperm. 



It is, of course, true that in all but the most dilute suspensions 

 the hydrogen ion concentration will in a short space of time be 

 the higher the more concentrated the suspension as a result of 

 the carbon dioxide produced by the sperm. This probably oc- 

 curred in Experiment 22, but it is improbable that this was the 

 only factor in the other experiments, and it certainly was not a 

 factor in the data that w r ill now be presented. 



In Experiments 31, 32 and 33 (p. 186) different amounts of 

 sperm from the same suspension were added to the same concen- 

 tration of eggs. These experiments are retabulated in order 

 that the percentage of eggs that were fertilized by different 

 amounts of sperm from the same suspension at the same time 

 can more easily be compared. When all of the eggs were not 

 fertilized by both concentrations of sperm the number of eggs 

 fertilized was always the greater the more spermatozoa were 

 added. 1 



This is not a new observation. It is the common experience 

 of investigators, and may be explained either by assuming that 

 in the greater concentration more sperm will on the average 

 arrive at the periphery of the egg with sufficient action (having 

 the dimensions of energy X time) to initiate development, or by 

 assuming that mass action of spermatozoa may be effective in 



1 It should be pointed out that whereas motility is unquestionably a mani- 

 festation of energy, the observation of motile spermatozoa at the periphery of an 

 unfertilized egg in no way indicates the physiological condition of the spermatozoa. 



