288 STUDIES ON BIOLUMINESCENCE. IX 



Dilute acetic acid added to concentrated luciferin gives a stringy 

 precipitate. If filtered off, the filtrate is slightly opalescent but 

 does not become more cloudy or precipitate if more acetic acid is 

 added. It gives a bright light if luciferase is added to it. The pre- 

 cipitate does not completely dissolve in water, but if washed with 

 water and suspended in water gives a fair light with luciferase. This 

 precipitate is probably a mucin containing some adsorbed luciferin. 

 In the luminous gland of Cypridina there is a material which stains 

 as does mucin and it would be found in the hot water extract of the 

 whole animal. The acetic acid precipitate does not form readily if 

 the luciferin solution is hot when acetic acid is added. A little dilute 

 NH4OH will dissolve the precipitate and it can be reprecipitated by 

 acetic acid. The filtrate from the acetic acid precipitation gives a 

 voluminous precipitate with phosphotungstic acid which does not 

 carry down all the luciferin unless a little HCl is also added, when 

 luciferin is completely precipitated and may be demonstrated in the 

 precipitate. 



Dilute HCl alone gives a precipitate with crude luciferin solution 

 but it almost completely dissolves in an excess of dilute HCl. 



Saturation of a solution of crude luciferin in presence of some NaCl 

 with carbon dioxide does not cause precipitation or an increase in 

 turbidity. 



Dilute trichloroacetic acid gives a stringy precipitate with crude 

 luciferin solution similar to that with acetic acid, but abundant lucif- 

 erin is found in the clear filtrate which gives no further precipitate 

 with trichloroacetic acid. These results are recorded in Table III. 



Hence neither luciferin nor luciferase is precipitated from crude 

 solution by dilute NH4OH or NaOH or by dilute acetic acid, and 

 neither of them can belong to the group of histones (precipitated by 

 dilute NH4OH) or mucins, or nucleoproteins, or such phosphoproteins 

 as caseinogen, which are precipitated by dilute acetic acid. A mucin 

 or nucleoprotein is precipitated from both crude luciferase and 

 luciferin solution by dilute acid and carries down some luciferase and 

 some luciferin in the adsorbed state. It is easy to demonstrate that 

 such an adsorption might occur. A solution of sodium caseinogenate 

 mixed with either luciferin or luciferase and precipitated with acetic 

 acid will carry down a considerable amount, but not all of the luciferin 



