STUDIES OF FERTILIZATION 



565 



the sea-water in which the fertihzations were made. The other 

 vertical columns give the percentages of eggs segmented for each 

 concentration of blood on the same horizontal level. The last 

 reading in each column gives the control, i.e., fertilizations made 

 in sea-water alone with the same amounts of the same eggs and 

 sperm used in the blood solutions. The eggs in the blood solutions 

 were washed in the same way as the controls prior to insemination. 



It will be noticed that in all these cases there is a marked re- 

 duction in the percentage of fertilizations when 5 per cent blood 

 is present in the sea-water, greater in some cases than in others, 

 which leads to the conclusion that the inhibitor is present in higher 

 concentrations in some samples of blood than in others. This 

 relation is dealt with below. In Experiments 1 and 2 of July 15, 

 and in the experiment of July 22, there will be noticed after the 

 first fall with increasing blood-concentration a rise and second 

 fall in the percentages of fertilizations as measured by cleavage 

 of the eggs. This is unquestionably of some significance, but I 

 have been unable to ascertain what its meaning may be. The 

 same phenomenon occurred in later experiments. 



