EGG SECRETIONS OF ARBACIA AND ASTERIAS 475 



reaction with this precipitate takes place rather quickly. At 

 the end of the two and a half hours it was found that the de- 

 crease in diameter of the drops amounted to between 10 per cent 

 and 23.5 per cent, with an average of 16.7 per cent. This would 

 indicate that the secretion could change the fat into a compound 

 soluble in water. 



3. The precipitation of specific elements from the egg secretion 

 and their properties. Of especial significance is the study of sub- 

 stances precipitated from egg secretions. It will be recalled 

 that neither Glaser nor the writer obtained a precipitate from the 

 egg secretion by boiling or adding absolute alcohol. Since, 

 however, the secretion was colloidal (not dialyzable), other 

 methods of precipitation were tried in 1915 and 1916. 



a. Precipitation of a sperm agglutinin. If the egg secretion of 

 Arbacia is saturated with crystals of pure (NH4)2S04, a whitish 

 flocculent precipitate is formed. This may be washed in sat- 

 urated ammonium sulphate solution and dissolved in either fresh 

 or sea-water. The solution causes reversible . agglutination of 

 sperm, while ammonium sulphate alone paralyzes but does not 

 agglutinate them. If the precipitate is dissolved in distilled 

 water and dialyzed in a collodian sac against distilled water or 

 running tap water until, as shown by testing with BaCL, all the 

 SO4 is removed, it still causes reversible agglutination of sperm. 

 This power is lost after a few days, probably because of bacterial 

 action. The precipitate may, however, be kept ten days or more 

 without losing its agglutinative power if covered by saturated 

 (NH4)2S04, which prevents the growth of bacteria. By this 

 method a solution may be obtained with greater agglutinating 

 power than the original egg extract. The method does not, 

 however, bring about complete precipitation of the sperm agglu- 

 tinin, as was shown by dialyzing and testing the filtrate obtained 

 after the addition of (NH4)2S04. This still caused agglutination. 

 This precipitate has no parthenogenetic power. 



b. Precipitation of a lipolysin. Since there were strong indi- 

 cations of the presence of lipase and perhaps other enzymo-, I 

 adapted a method used by Robertson ('12) to obtain an enzyme 

 from blood serum. Eight volumes of fertilizin and four volumes 



