324 T. H. MORGAN. 



blood of the same individual does not affect the sperm so that it 

 fails to cross-fertilize. 



Experiment 5. - - The eggs were put into the blood of another 

 individual for twenty minutes, and then removed to sea water, 

 and their own sperm added. No self-fertilization followed, al- 

 though direct cross-fertilization gave 70 percent, for the B-eggs, 

 and 100 per cent, for the A- eggs, showing that both eggs and 

 and sperm were good. 



Experiment 6. In order to test whether the blood itself may 

 not sometimes become contaminated with its own sperm, one 

 portion of the blood of A was diluted with sea water, and B-eggs 

 were then put into it. In one case a few eggs segmented, show- 

 ing that contamination may occur. Heating the blood would, 

 of course, kill the sperm, but this would open the experiment to the 

 objection that the composition of the blood might be so affected 

 that the postulated soluble substance is destroyed. Since most of 

 the experiments gave negative results the contamination of the 

 blood, if it occurred, would not vitiate such results ; but if the re- 

 sults had been positive this possibility would havehad to be care- 

 fully reckoned with. 



EFFECTS OF SHAKING. 



It seems not improbable that the covering of test-cells might 

 be the immediate cause of the lack of power to self-fertilize. 

 Therefore I tried the effect of shaking them off, and adding sperm 

 of the same individual to the denuded eggs. 



Experiment 7. In this case only one egg out of 200 seg- 

 mented, while 400 of the same eggs unshaken showed no seg- 

 mentation. 



Experiment S. - - In another case about 20 per cent, of the 

 shaken eggs segmented, but some of those that segmented had 

 still some of the follicle cells attached. In another instance 8 

 out of a total of 40, or 20 per cent., segmented. 



These results show unmistakeably that shaking increases the 

 percentage of self-fertilizations that take place, but whether on 

 account of the removal of the follicle cells, or from some other 

 change induced in the eggs is not certain. 



Experiment 9. - - In this case none of the shaken eggs seg- 

 mented ; although the crossed eggs gave 50 per cent, in one 



