I]. THE CHEMICAL NATURE OF CYPRIDINA LUCIFERIN 
AND CYPRIDINA LUCIFERASE. 
PREPARATION OF MATERIAL. 
The living animals are dried quickly in desiccators over CaCl, and 
may then be kept indefinitely in well-stoppered bottles containing a 
few lumps of CaCl, to remove any dampness in the air contained in the 
bottle. As the Cypridine dry, crystals of the salts of sea-water form 
upon them. These salts are hygroscopic and take up water, which 
results in a slow deterioration of the material unless precautions are 
taken to prevent access of water-vapor. Some of the salt and much of 
the débris of the animal’s shell may be removed by a purely mechanical 
method. The whole Cypridine are finely ground in a mortar and the 
powder shaken with carbon tetrachloride. On standing, a layer of 
powder which contains most of the photogenic material, fragments of 
muscle, etc., is found floating at the surface of the CCl,, while a layer of 
greater specific gravity at the bottom is found to contain very little 
photogenic material but much of the ground-up pieces of the shell. 
The CCl, extracts some of the fatty material and the remainder (with 
exception of lecithin) can be removed from the powdered animals by 
ether or petroleum ether in a Soxhlet extractor. These fat solvents do 
not dissolve or injure the photogenic substances in any way, although 
they are not sufficient for removal of all the lecithin from dried tissues. 
For this it is necessary to extract with hot alcohol, but as luciferin is 
soluble in absolute alcohol and more so in water-aleohol mixtures, we 
ean not employ alcohol for this purpose. The lecithin in tissues which 
can not be extracted with ether is probably in combination with pro- 
teins. The treatment described above gives us a powder which lights 
briliantly if moistened with water, both of the photogenic substances 
going into solution. It serves as the raw material for the isolation of 
luciferin and luciferase. <A series of extractions of the dried material 
has also been made to determine the solubility of luciferin and luciferase 
in solvents other than water. Luciferase proved to be insoluble in all 
that were tried, but luciferin was soluble in many (see p. 109), although 
these non-aqueous solvents are less well adapted for its isolation than 
water. Accordingly both luciferin and luciferase have been extracted 
with pure water (distilled water or tap water) and purified by precipi- 
tation and re-solution. 
From the dried, powdered, fat-free Cypridine an extract may be pre- 
pared with distilled water which contains luciferin, luciferase, all the 
proteins of the animal soluble in water, salts, and other water-soluble 
material. The extract, filtered through filter-paper, is yellow-colored 
and slightly opalescent and glows for some time. The light finally dis- 
appears, due to the oxidation of the luciferin. There is no change of 
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