SELF-FERTILIZATION IN CIONA. 325 



case, and 100 in another showing that the eggs and the sperm 

 were good. 



EFFECT OF FOLLICLE WATER. 



If some substance in the follicle cells excites cross-fertilization, 

 then it seemed likely that the water in which the eggs had been 

 violently shaken, so that the follicle cells broke apart, might act 

 on the sperm or eggs of another individual, and cause self-ferti- 

 lization. This was tried in a few cases. 



Experiment 10. - - In one case five per cent, of the eggs divided ; 

 in three cases there were no divisions ; in another case 70 per 

 cent. divided, but went only into the two- or four-cell stages, 

 which seemed to show that something unusual had taken place, 

 and that the results were not due to the follicle water. There is, 

 in fact, a source of contamination in this experiment that may 

 fully account for all the cases observed. In removing the eggs 

 from the oviduct some of the sperm from the vas deferens may 

 be accidently squeezed out and become mixed with the eggs, and 

 remaining in the follicle water fertilize the other eggs. The 

 shaking might injure the sperm, but those that escaped might 

 still suffice. The peculiar segmentation in the case in which a 

 considerable number of eggs segmented may have been due, in 

 fact, to the injury to the sperm. Separate experiments must be 

 undertaken to test this possibility. The negative results in these 

 cases are probably the more significant. 



EFFECTS OF STANDING. 



Experiment 1 1. - - The relative age of the eggs might, it seemed 

 to me, be a factor in the result ; also by standing in sea water the 

 substance that prevents self-fertilization might be washed out. 

 To test these possibilities, eggs were removed and kept for eight 

 hours in one case in sea water and then self-fertilized with their 

 own sperm that had remained in the animal. No results fol- 

 lowed. That the eggs are not injured by standing in sea water 

 was shown by their power to become cross-fertilized even after 



24 hours. 



EFFECTS OF BURSTING THE EGGS. 



Experiment 12. By compressing the eggs between a cover 

 slip and a slide they can be burst in some cases. I attempted 



