134 PROBLEMS OF FERTILIZATION 



has pointed out, that the postulated fertilizing sub- 

 stance of the spermatozoon requires the motive power 

 of the spermatozoon to make it effective against the 

 egg, which is the only indicator, and that it will not 

 act in solution; it is also possible that it is labile in 

 solution, or that methods employed in the endeavor to 

 isolate it have been too brutal. We have seen (pp. 1 12 ff .) 

 that spermatozoa carry an agglutinable substance which 

 is lost after reaction with the agglutinating substance of 

 the egg; the presence of such a substance could not be 

 demonstrated by mere isolation methods. 



The writer (191 5) has employed another method for 

 demonstrating the existence of such a substance. He 

 showed that the rate of loss of fertilizing power of 

 sperm suspensions of ^r^aaa is inversely proportional to 

 their concentration and that in great dilutions the loss 

 of fertilizing power is many times more rapid than the 

 loss of motility. This was ascribed to loss of a specific 

 substance by the spermatozoon, for the other factors 

 for successful insemination were maintained constant. 

 Other observers (e.g., Schiicking, 1903, and Glaser, 

 1 9 14) have noted that several spermatozoa appear to 

 be needed for fertilization of a single ovum, because 

 fertilization usually failed under the conditions of their 

 experiments unless a number of spermatozoa were pres- 

 ent simultaneously in the jelly around the egg. Glaser 

 postulated a mass effect of spermatozoa in fertilization 

 as well as an individual effect to explain this. The 

 writer could, however, demonstrate that mass effect is 

 not necessary if the sperm suspensions are sufficiently 

 fresh, and that the appearance observed by Schiicking and 

 Glaser is found only with suspensions not perfectly fresh. 



