144 PHOTOGENIC REACTION IN CYPEIDINA 



quite a marked reducing action. Acid thus favors reduction and 

 hinders oxidation, while alkah favors oxidation and hinders reduction 

 of the oxyluciferin. 



While I have not studied the properties of oxyluciferin so fully as 

 those of luciferin, as far as I can judge both substances give the same 

 general reactions and possess identical properties. If we make a con- 

 centrated hot water extract of Cypridina, it will contain all the sub- 

 stances of the animal soluble in hot water and not coagulated by heat 

 and may be spoken of as crude luciferin solution. If air is bubbled 

 through this solution for some time, all the luciferin is oxidized and 

 it may then be spoken of as crude oxyluciferin solution. Both crude 

 luciferin and crude oxyluciferin solution are yellow in color, but I do 

 not believe that either luciferin or oxyluciferin is yellow in color be- 

 cause an ether or benzene extract of Cypridina is also yellow although 

 luciferase, luciferin, and oxyluciferin are all insoluble in ether and 

 benzene. The yellow pigment which can be observed to make up 

 part of the luminous gland of Cypridina is not luciferin or luciferase. 

 It may be a pigment related to urochrome. 



When tests are applied and precipitating reagents are added to crude 

 luciferin and crude oxyluciferin solution they give identical results in 

 each case. Thus if crude luciferin is saturated with (NH4)2S04 or 

 MgS04, a flocculent precipitate forms which may be demonstrated to 

 contain most of the luciferin. Oxyluciferin solution also gives 

 flocculent precipitates on saturation with (NH4)2S04 and MgS04 and 

 these contain most of the oxyluciferin. To demonstrate this the 

 precipitates, after washing, are dissolved in a small amount of water 

 mixed with fresh milk (or frog muscle suspension) and allowed to 

 stand in a stoppered tube for 24 hours. If any oxyluciferin is pres- 

 ent it will be reduced to luciferin and give light when luciferase is 

 added. One-half saturation with (NH4)2S04 or MgS04 or saturation 

 with NaCl salts out no material from either crude luciferin or oxyluci- 

 ferin solution. Picric acid gives no precipitate but only an opales- 

 cence in both cases. In a similar manner it may be shown that most 

 of the oxyluciferin is precipitated by phosphotungstic acid but not 

 by acetic acid or CO2, in this respect also agreeing with the behavior 

 of luciferin. Like luciferin the oxyluciferin will pass porcelain fil- 

 ters, dialyze through parchment or' collodion membranes, is soluble 



