136 PROBLEMS OF FERTILIZATION 



sea-water was always kept to guard against chance 

 fertilizations. To illustrate: the last four determina- 

 tions of the curve were made as follows: In four crystal- 

 lization dishes were placed 1,000 c.c. sea-water (^4), 

 3,000 c.c. sea- water (B), 1,000 c.c. sea- water (C), 3,000 

 c.c. sea-water (D). To each was added 2 c.c. of a 

 washed egg suspension. The sperm was then prepared 

 as follows: (i) one drop dry sperm to 3.3 c.c. sea- 

 water at 9:43 A.M. = I per cent; (2) i c.c. sperm i 

 to 99 c.c. sea-water at 9:43! A.M. = 1/100 per cent; 

 (3) i c.c. sperm i to 999 c.c. sea-water at 9:45! A.M. = 

 i/ 1,000 per cent. To A was added i drop sperm 2 

 (i/ioo per cent) at 9:43!; to B one drop sperm 2 

 (i/ioo per cent) at 9 : 44 ; to C one drop sperm 3 (1/1,000 

 per cent) at 9:45!; to D one drop sperm 3 (1/1,000 per 

 cent) at 9:45!. An assistant stirred in the sperm thor- 

 oughly as added. The sperm concentration in A was 

 therefore 1/100X1/30X1/1,000 = 1/3,000,000 per cent; 

 in B it was 1/9,000,000 per cent; in C, 1/30,000,000 

 per cent; in D, 1/90,000,000 per cent; 1/3,000,000 

 per cent falls between 21 and 22 on the scale, and the 

 others as shown. The exact times of mixing the sperm 

 are given because, as will appear beyond, time is an 

 extremely important factor with reference to fertilizing 

 power. 



To appreciate the extent of the greatest dilution it 

 may be said that beyond a dilution of 1/10,000 per cent 

 (between 13 and 14 on the scale) one can rarely find a 

 single spermatozoon in the jelly of the fertilized eggs. 

 At about 1/2,000 per cent (n on the scale) the sperm 

 suspension does not even appear opalescent. We may 

 therefore feel reasonably sure that beyond about 14 or 



