SELF-FERTILIZATION IN CIONA. 323 



Experiment j. - - In this experiment the eggs (instead of the 

 sperm) were soaked for a short time in the extract of the ovary of 

 another individual in order to see if they might not acquire the 

 power to become fertilized by the sperm if this were then added. 



The A-eggs were soaked in the extract of the ovary of B about 

 I 5 minutes. The A-sperm was added to sea water, and left for 

 5, 10 and 15 minutes. Then the A-eggs were added to the 

 A-sperm solutions. No eggs segmented, but neither did the eggs 

 in the check experiment in sea water, showing that the eggs or the 

 sperm were poor, or else incompatible. In the check experi- 

 ment (B-eggs in extract of A-ovary), however, 100 per cent, of 

 the B-eggs were fertilized by the A-sperm. This also happened 

 in the cross in sea water. Here the A-extract did not prevent 

 the B-eggs from being cross-fertilized by A-sperm. The solution 

 must have been sufficiently dilute for fertilization to take place. 



Experiment 4. In this case the mantle was removed, and the 

 body wall slightly cut so that the heart protruded, which was 

 cut open and the blood collected. The eggs of another indi- 

 vidual were then put into the blood. There is here a possible 

 source of contamination, since some of the follicles of the testis 

 may be broken, and allow some of the sperm to get into the 

 blood. The results of one experiment of this sort were as 

 follows : 



In Blood. Diluted Later. 



n , 



o 40% 



o 70 



The check crosses carried out in sea water gave for the A- 

 eggs (B-sperm) 90 per cent, of cases of segmentation, and for 

 the B-eggs (A-sperm) 50 per cent. The first two combinations 

 (i) and (2) of the table, gave no results in the blood itself, but 

 when the blood was diluted they gave nearly the same percent- 

 ages as in sea water. In the second cases the dilution was prob- 

 ably insufficient. Thus it is shown that the undiluted blood in- 

 terferes with the fertilization, but on the other hand the diluted 



