E. NEWTON HARVEY 279 



erin and luciferase; weakly, in saturated MgS04 which dissolves 

 some luciferin but very little luciferase; and not at all in saturated 

 (NH4)2S04 which dissolves no luciferase. On filtering the saturated 

 (NH4)2S04 extract of dry Cypridince and pouring this into water, no 

 light appears, but if luciferase is now added, a faint light appears, 

 showing that a small amount of luciferin has gone into solution. 

 These results are summarized in Table II. 



Although we ordinarily think of the proteins as the substances, par 

 excellence, capable of being salted out of solution, the property is char- 

 acteristic of many emulsion colloids, notably soaps, polysaccharides, 

 and phospholipins. However, neither luciferase nor luciferin is a 

 soap because they are not precipitated by CaCl2; nor phospho- or 

 galactolipins, because they are both insoluble in ether and benzene, 

 hot or cold. It is possible that they are of polysaccharide nature as 

 starch and glycogen are nearly if not completely precipitated by 

 saturating their solution with (NH4)2S04. But the polysaccharides 

 are not precipitated by phospho tungstic acid, whereas luciferase is 

 completely precipitated and luciferin very nearly completely precipi- 

 tated (see p. 283). 



The evidence from salting out experiments indicates that both 

 luciferin and luciferase are proteins, the former on the border-line 

 between proteoses and peptones, the latter a more complicated pro- 

 tein but not a globulin. Dubois^ finds Pholas luciferin completely 

 precipitated by saturation with (NH4)2S04 but not by MgS04 or 

 NaCl. 



Alcohol and Acetone. 



If strong ethyl alcohol or acetone is added to a solution of crude 

 luciferase, an abundant precipitate forms. This precipitate is found 

 to contain the luciferase which is separated completely from solu- 

 tion by alcohol between 50 and 60 per cent, and by acetone between 

 70 and 80 per cent. We are dealing in both cases with a precipitation 

 and not a coagulation of luciferase. The precipitates partially re- 

 dissolve in water and if the solution is filtered luciferase is found in 

 the filtrate. Indeed, the precipitates from addition of alcohol or 

 acetone to crude luciferase may stand under alcohol (95 per cent) or 

 acetone (90 per cent) respectively for 35 days without complete de- 



