266 Studies in the Phjisiology of Fertilization 



in the last experiments, the segmentation rates were identical in each 

 pair of fertilizations for eggs in water and in egg-extract. 



Finally the experiment shows that the extract has an immediate 

 effect in raising the percentage, since the first pair of fertilizations was 

 made as soon as the lots of eggs had been tried out into water and 

 extract. The falling off of the percentages in subsequent fertilizations 

 was less rapid in the eggs in extract than in those in water. 



2. Cross-fertilization of C'iona in boiled egg-e.rtract. 



An experiment was made (21.3.2) to discover whether heating the 

 egg-extract altered its effect on fertilization. 



Extract was made of C eggs and a portion heated to boiling-point. 

 Approximately equal numbers of j4 eggs were placed in (1) 12 cc. water, 

 (2) 12 cc. unboiled egg-extract, (3) 12 cc. boiled egg-extract. After 

 33 minutes one drop of diluted sperm-suspension b was added to each. 



TABLE III. 



Water Extract Boiled extract 

 Cross: Ajb, C extract 19 8 



The counts of eggs fertilized show that both boiled and unboiled 

 extracts raised the percentages to an almost equal extent. The difference 

 of 1°/^ between the two Ijes within the limits of experimental error. 



Thus the value of the egg-extract is not destroyed by boiling for a 

 short time. No further experiments were made on the stability of the 

 extract as there were more imjjortant questions to be decided first. 



3. Cross-fertilization of Ascidia in egg-extract. 



The question then arose as to whether the effect of egg-extract on 

 fertilization percentages was confined to Ciona or was to be found in 

 other forms as well. The next animal to be tried was Ascidia mentula. 



Approximately equal numbers of eggs D were placed in each of 

 (1) two dishes containing 17 cc. of sea- water, (2) two dishes containing 

 17 cc. C egg-extract. Thirty-three minutes afterwards, two drops of a 

 weak sperm-suspension c were added (1) to a dish of water containing 

 eggs, (2) to a dish of egg-extract containing eggs. At the same time 

 five drops of a stronger sperm-suspension c were added (1) to a tlish of 

 water containing eggs, (2) to a dish of egg-extract containing eggs. 

 The experiment was thus double, the comparison being made first with 

 weaker and then with stronger sperm. 



