STUDIES OF FERTILIZATION. 



241 



power increases with dilution, i. e., the effect of time varies in- 

 versely to concentration of sperm. This is brought out very 

 clearly by the following curves (Fig. 3) of loss of fertilizing 



o 5 10 15 20 25 30 35 40 45 50 55 60 6s 70 



I 2 I \ 



Curve 3. 



power of sperm suspensions at different concentrations. The 

 abscissae represent age of sperm suspensions in minutes; the 

 ordinates represent fertilizing power as expressed in percentages 

 of segmenting eggs. Each curve stands for a given sperm 

 dilution. Curve i represents loss of fertilizing power of a 

 1/300 per cent, sperm suspension, curve 2 of a 1/3000 per cent., 

 curve 3 of a 1/30,000 per cent, and curve 4 of a 1/120,000 per cent, 

 sperm suspension. 



B. On August 6, I prepared a series of seven sperm dilutions 

 in powers of 4 from i per cent, to 1/4096 per cent. Each of these 

 was then used to fertilize a measured quantity of egg-suspension 

 at the intervals given in Table III. 



For the fertilizations 10 c.c. sea-water was measured out in 

 advance in Syracuse crystals and 5 drops of a 5 per cent, egg 

 suspension added to each. For each fertilization i drop of sperm 

 was added and stirred in. It will be observed that i per cent, 

 sperm lost none of its fertilizing power so far as this test went; 

 1/4 per cent, fell off from 96.5 per cent, to 16.3 per cent.; 1/16 

 per cent, from 46.5 per cent, to o; 1/64 per cent, from 0.5 per 

 cent, to o in the second place ; whereas the greatest dilutions did 



