STUDIES OF FERTILIZATION. 



245 



per cent. But it was only from about 1/500 per cent, down that 

 any considerable effect was observed within the range of egg 

 concentration employed. 



The method of the experiments tabulated (Table IV.) may be 

 given for 1/500 per cent, sperm as it was the same for the others 

 August 31: A quantity of 1/500 per cent, sperm suspension was 

 freshly prepared 10.54.30 A.M., 2 c.c. of this was then placed 

 in each of seven crystals (1-7). From 10.56.30 to 10.59 A.M. 

 eggs were added as follows: to i, one drop of a 1.75 per cent, 

 egg-suspension, to 2 two drops, to 3 four drops, to 4 eight drops, 

 to 5 sixteen drops, to 6 one c-.c, to 7 two c.c. The numbers in 

 the table give the percentages of segmented eggs. The tests 

 with 1/1,000 per cent, and 1/2,000 per cent, sperm were made with 

 the same egg suspension. For the tests with 1/4,000 per cent, 

 and 1/8,000 per cent, sperm a 3.3 per cent, egg-suspension was 

 used. Thus for each series the egg-concentration is approxi- 

 mately doubled in successive numbers of the series (in No. 7 = 64 

 times No. i). 



Table IV. 



Effect of Egg-concentration on the Fertilizing Power of Sperm Sus- 

 pensions. 



The percentages of fertilization fall off in each of these sperm 

 suspensions with increase of egg-concentration, and the amount of 

 falling off increases in general with the dilution of the sperm. 

 There was certainly no numerical deficiency of spermatozoa in 

 the highest egg-concentrations; the reason for the falling off 

 therefore appears rather obscure, and as it is not involved in the 

 present problem, I shall not discuss it here. But as the egg- 

 concentration employed in any of the preceding experiments 

 did not exceed that of column 3, and the same egg-concentration 



