MASS PHYSIOLOGY OF SPERMATOZOA 



^65 



relation to dilution is shown in Figure 25, taken from Lillie and 

 Just, in which the ordinates give percentage of eggs fertilized and 

 the abscissas give a geometrical series of dilutions of i per cent 

 sperm in powers of 2. 



Lillie holds that fertilizmg power of the sperm vanishes before 

 motility, and that the spermatozoa tend to lose their fertilizing 

 ability in proportion to dilution, apparently because of the greater 

 speed of diffusion from the spermatozoa of some substance or sub- 

 stances necessary for fertilization. Obviously, this diffusion gradi- 



10 11 12 IJ I* 15 16 17 18 19 20 21 22 ?3 Z4 25 26 27 



Fig. 25. — Logarithmic curv-es showing the fertilizing power of diUitions of Arbacia 

 sperm. The vertical axis shows percentages of eggs fertilized; the horizontal axis 

 gives dilutions of sperm in powers of 2. Graph a, perfectly fresh sperm; graph b, 

 sperm suspensions 20 minutes old. (After Lillie and Just, 1924.) 



ent would be steeper the less concentrated the sperm suspension; 

 hence the length of functional life would be shorter. 



Hinrichs (1926a), after producing further supporting evidence 

 from the greater resistance shown by more concentrated sperm sus- 

 pensions to ultra-violet radiation, sums up the situation as follows: 



"Time and dilution are both known to be factors aft'ecting the 

 fertilizing power of Arbacia sperm (F. R. Lillie, 191 5). Drzewina 

 and Bohn (ig2T,b) also showed dilution to be a factor in the suscep- 

 tibility of sea urchin sperm to the combined action of neutral red 

 and light. Motihty and fertilizing power were lost more quickly in 

 dilute than in concentrated sperm suspensions. Usually loss of 

 motility is associated with loss of fertilizing power, but the two do 

 not exactly parallel each other. Fertilizing power is not a function 



