STUDIES OF FERTILIZATION. 239 



explanation for two reasons: in the first place the time from 

 preparation of the original i per cent, sperm suspension to that 

 of addition of eggs is usually less than twenty-five minutes, which 

 is usually considered too short a time for injury to sperm; and 

 in the second place, after the addition of eggs to the sperm- 

 dilution series, in several control experiments the original i 

 per cent, sperm suspension was shown to be capable of fertilizing 

 at 1/30,000 of I per cent. (1/2^^ ca.) by addition to eggs in sea- 

 water. // the sperm suspensions lose their fertilizing power with 

 time, it must he that the significance of time in this respect varies 

 inversely to concentration. As soon as such a proposition is 

 formulated it is easily tested experimentally, and this was done 

 in a thorough fashion. 



4. Time as a Factor in the Fertilizing Power of Sperm Suspensions 

 of Different Concentrations . 

 The experiments under this head were performed in three ways: 

 A. A considerable quantity of the sperm suspension to be 

 tested was made up, and divided in several equal parts in a series 

 of bowls; measured equal quantites of the same egg-suspension 

 were then added to members of the series at definite time inter- 

 vals. This method was followed for sperm dilutions from 1/300 

 per cent, (between 8 and 9 in the scale) down. B. Measured 

 amounts of the more concentrated sperm suspensions were added 

 at time intervals to measured quantities of eggs in equal amounts 

 of sea-water. C. Finally, to control the data in section 3, a 

 series of sperm suspensions, made by successive half dilutions 

 as in section 3, was divided in two equal series, and eggs were 

 added at once to the one series, and after a time interval to the 

 second. 



A. The following table gives the data under method A. The 

 figures at the head of each vertical column give the sperm dilu- 

 tion in fractions of the i per cent, sperm suspension; below is 

 given the place of such a sperm suspension in the scale of powers 

 of 2. The figures in the columns give the percentages of fertiliza- 

 tions for inseminations made at the time (age of the suspensions 

 in minutes) indicated at the left. To illustrate the method of 

 experimentation for one column which will serve for all the rest, 



