SELF-FERTILIZATION IN CIONA. 3 I 5 



crossed with all the different kinds of sperm, and self-fertilization 

 was also tried in each case. The self- fertilized lots form a diag- 

 onal line across the tables. In only a single case out of the many 

 hundreds of eggs mixed with their own sperm did fertilization 

 occur. It is needless, perhaps, to add that separate scissors, 

 pipettes, etc., were used for each individual. In each experiment 

 there were thirty-six fertilizations made, of which thirty were 

 crosses, and six self-fertilizations. In the eight experiments that 

 I carried out there were therefore 240 cross experiments, which, 

 if not a very extensive series, yet ought to suffice to show the 

 main points. The percentages given in the following tables indi- 

 cate the proportionate number of eggs in each set that segmented ; 

 the estimated number are approximations only, and not, in all 

 cases, the results of exact counts. 



TABLE I. 



An analysis of the results shown by this table leads to the fol- 

 lowing conclusions. The A-eggs were in good condition (or 

 more briefly were "good"), since with "good" sperm 90 per 

 cent, of them were fertilized in one case. The B-eggs were 

 poor, the C-eggs excellent, the D-eggs very good, the E and F- 

 eggs were poor. The a-sperm was excellent, as seen in C a ; the 

 b, c, d, e-sperm were also excellent ; but the f-sperm was very 

 poor, since not a single egg in any of the sets was fertilized by it. 

 From the results of this table it looks as though good sperm 

 would always fertilize good eggs of any other individual, but 

 there are even here three significant exceptions to this statement. 

 The d-sperm gave poor results with A-eggs (A d ), although other 

 experiments show that both the sperm and the eggs of these two 

 individuals were good. The other cases are those of A e and D e , 

 in which the e-sperm failed completely with the A and with the 

 D-eggs, although with the C-eggs it gave 75 per cent, of seg- 

 menting eggs. 



