EGG-SECRETIONS OF ARBACIA AND ASTERIAS. 373 



theory of fertilization (*I3 2 ). Analyses by other methods were 

 attempted. 



It is altogether likely, and in the case of the Nereis-Arbacia 

 hetero-agglutination, definitely proved, that the egg-secretion 

 contains more than one substance. The problem therefore 

 presents itself of isolating these bodies. A first step toward 

 orientation has been made by means of certain qualitative chem- 

 ical tests. 



The method of securing egg-secretion finally adopted was 

 suggested to me personally by Dr. F. R. Lillie, and consists in 

 adding to a certain number of "dry" eggs, double their volume 

 of sea-water, and with occasional slight agitation, allowing ten 

 minutes to elapse. At the end of this time the ova were pre- 

 cipitated by 100 revolutions of the centrifuge, and the super- 

 natant fluid, a clear, golden liquid in the case of Arbacia, or 

 whitish and opalescent in the case of Asterias, was usually care- 

 fully decanted without filtration through paper. Such solutions 

 I have adopted as standard. With the Arbacia secretion the 

 following tests were made: 



I. The solution is gold-yellow in color and clear. 

 '2. The solution is neutral to litmus. 



3. Upon cooling to o no change was noticeable. 



4. Upon boiling the color becomes faintly purple. 



5. The purple coloring matter may be removed at least in 

 part if white of egg is allowed to coagulate in the boiling solution. 



6. No acid-insoluble precipitate is formed upon the addition 

 of n/io NaOH. 



7. i or 2 drops cone. HC1 produced faint cloudiness which 

 became more distinct on standing. 



8. The addition of alcohol produced no visible change. 



9. Millon gave a white precipitate with no color change on 

 boiling. 



10. The biuret test was negative. 



II. HNO 3 gave no ring but a faint cloudiness. 



12. The xanthoproteic test gave no precipitate, but the solution 

 turned distinctly yellow. 



13. The Adamkiewicz test was negative. 



14. Fehling gave no reduction. 



