EFFECT OF EXTRACTS UPON DEVELOPING EGGS. 83 



with the results obtained by the use of unboiled extracts. Boil- 

 ing the suspension to be used for extract was done rot only to 

 destroy bacteria, but also to take into account the bare possibility 

 that substances in the larvse which were evidently not soluble in 

 cold sea water might go into solution in hot water. 



Note. Cleavage rate given in terms of minutes which elapsed 

 between insemination and the appearance of the first 2-, or 4-cell 

 stage. 



Later Development and Fate. Development in all the cultures 

 was nearly parallel through the blastula stage except in F' ' , in 

 which the eggs failed to segment at all. From the blastula to the 

 pluteus stage the cultures containing extract were very slightly 

 retarded as compared with the control A'. There was also a very 

 slight retardation in the cultures containing the specified amounts 

 of blastula water. In all cases, as usual, the retardation resulted 

 in the production of plutei varying slightly from the normal in 

 many respects, but yet producing no one definite type of abnormal- 

 ity. 



Boiled extracts of gastrula and early plutei were made also, 

 but the results obtained were entirely similar to those indicated 

 above. 



Conclusion. Boiling the extract appears to reduce, if not to 

 eliminate entirely the amount of retardation in the cultures. 



Two other methods of making extract in a solution of sea 

 water were tried, since it is obvious that if the extracts were made 

 in a solution of the same osmotic pressure as that in which the 

 eggs developed, that is, sea water, the problem would be much 

 simplified. 



The first variation in the method of making the extract was as 

 follows: The eggs were centrifuged, and after the supernatant 

 fluid had been decanted they were placed in a celloidin tube con- 

 taining distilled water and set in a beaker of sea water. The eggs 

 swelled and burst, presumably setting free substances which, if 

 soluble in water, would dialyze through the celloidin tube into the 

 sea water in the beaker. Extract made in this way was used, but 

 the results obtained were not positive enough to be of value with- 

 out further experiment. The " double sea water " method was 

 also employed in one series of experiments with equally incon- 



