H. M. FiTCHS 235 



and 3 there was an excess of sperm throvighout in the cross-fertiliza- 

 tions, 100% of eggs segmenting every time. In Exps. 1, 4 and 5, 

 however, the percentages fell — in the last two, rapidly. 



TABLE V. 



Fert. Fert. Fert. Fert. 



3.50 4.50 5.45 6.50 



Cut outl 2.55-3.10 p.m. (19-5"C.) (20"C.) (20"C.) (20-5'C.) 



Exp. 1 Self-fert. Aja, 3 cc. thick sperm, 10 cc. water 4 6 9 



Cross-fert. Z)/a, 1 cc. dilute sperm, 10 cc. water 100 100 79 89- 



Exp. 2. Self-fert. Clc 3 cc. thick sperm, 10 cc. water 21 23 — 12 



Cross-fert. F/c, Ice. dilute sperm: 10 cc. water 100 100 — 100 



Fert. Fert. Fert. Fert. Fert 



Cutout 1.0— 1.10 p.m. 1.45 2.30 3.15 4.0 4.44 



Exp. 3. Self-fert. G/fl, 3 cc. thick sperm, 10 cc. water 4 23 75 78 83 



Cross-fert. if /.17, 1 cc. dilute sperm, 10 cc. water 100 100 100 100 100 



Fert. Fert. Fert. Fert. Pert. Fert. 



12 20 1.20 2 20 3.20 4'20 5'20' 

 Cut out 11.45-11. 55 am. (18°C.) (IVC.) (18°C.) (18° C.) (18°C.) {18-5°C.) 

 Exp. 4. 



Self-fert. 7//, 3 cc. thick sperm, 10 cc. water... <1<1 



Cross-fert. J/t, 4 drops dilute sperm, lOcc. water 97 96 80 23 2 



Fert. Fert. Fert. Fert. Fert. 



12.20 1.20 2.20 3.20 420 



Cut out 11.30-11.45a.m. (18°C.) (18°C.) (18-6°C.) (18-5-C.) (19° C.) 

 Exp. 5. 



Self-fert. A'/fc, 4 cc. thick sperm, 10 cc. water ... 6 10 29 1 <1 



Cross-fert. 7j/i, 2 drops dilute sperm, 10 cc. water 100 05 23 8 



From the experiments already described on the length of time that 

 sperm and eggs remain capable of fertilizing, it appeared that the sperm 

 loses its capability rapidly, while the eggs "go off" much more slowly. 

 From this it would seem that the falling off of the cross-fertilization 

 percentages in Exps. 1, 4 and 5 is to be attributed to the failure of the 

 sperm rather than of the eggs. 



From a comparison of the coiTCsponding self- and cross-fertilizations 

 in Exps. 1, 4 or 5 it seems that the self-fertilization percentages continue 

 to increase until the sperm begins to fail (as indicated by the decreasing 

 cross-fertilization percentages) after which they decrease again. In 

 Exp. 3, where the cross-fertilization percentages show that the sperm 

 did not commence to lose its fertilizing power during the progress of 

 the experiment, the proportions of eggs self-fertilized continued, to rise 

 steadily. 



1 By "cut out" is meant tlie time at which the genital products were removed from the 

 duets. 



" Tliis last fertilization showed much polyspermy, which may account for the irregu- 

 larity in the percentages. In all other cases recorded in this paper segmentation was 

 regular, unless otherwise mentioned. 



