THE PHYSIOLOGY OF FERTILIZATION 



IOO 



90 

 80 

 70 

 60 



50 

 40 

 30 

 20 



8_ > 10 JI 



\ 



15 on the scale no egg will receive more than one sper- 

 matozoon. 



In further elucidation of the curve (Fig. 16) I may 

 say that the critical (steep) part was covered by several 

 determinations for each point. Thus there are five 

 determinations averaged for the positions between 13 

 and 15, seven between 15 and 18, five between 18 and 

 20, and six between 20 and 21. The determinations 

 beyond 21 are single deter- 

 minations. For the first 

 part of the curve up to 

 13 there are numerous 

 determinations. There 

 are great variations in 

 the single determina- 

 tions compared with one 

 another; these averages 

 must therefore be re- FIG. 17. Curve of fertilizing power 



garded only as approxi- of sperm suspensions of Arbacia about 

 mate values. With a 20 minutes old. Ordinates and ab- 

 rr . scissae as in Fig. 16. 



sufficiently large number 



of determinations the irregularities between 15 and 17 

 and between 19 and 22 would no doubt disappear. But 

 it is improbable that the general form of the curve 

 would undergo any essential change even with a much 

 more extensive series of determinations. 



If now we compare this curve of fertilization with 

 perfectly fresh sperm with sperm suspensions about 

 twenty minutes old we get the result shown in Fig. 17. 

 It will be seen that fertilizing power ceases at | 10 after 

 thirty minutes. If now one determines by compari- 

 son the rate of complete loss of fertilizing power of 



