178 Papers from the Department of Marine Biology. 



many non-luminous animals. It will also give light if mixed with 

 many pure substances, as chloroform, ether, benzol, thymol, saponin, 

 oleic acid, atropin, NaCl, and others. Since most of the above sub- 

 stances could not possibly be oxidized by the luciferase, I conclude 

 that they cause in some way the giving out of light in what Dubois 

 terms luciferase. On this view luciferase is the source of the light and 

 the luciferin (in the boiled extract of Cypridina) is something which 

 causes the luciferase to emit light. 



The substances causing the emission of light from a concentrated 

 solution of luciferase are similar to those producing cytolysis of cells, 

 and I have considered the possibility that the concentrated extract 

 might contain fragments of the luminous gland-cells which cytolyze 

 with light-production or possibly granules which dissolve with light- 

 production, as described in many other forms, and as especially prom- 

 inent in the juice of Cavernularia. I am, however, convinced that there 

 are in the extract of cypridinas which will give light with unoxidizable 

 substances no cell fragments present and no granules above those of 

 submicroscopic colloidal dimensions, for the following reasons: 



First, the light is always perfectly homogeneous and in marked con- 

 trast to the points of light of Cavernularia juice, where visible granules 

 and cell fragments do occur. 



Second, Cypridina extract (luciferase) will give light with thymol, 

 butyl alcohol, or NaCl crystals after filtration through a Chamberland 

 or a Berkefeld filter, which removes all cell fragments. 



PHOTOPHELEIN AND PHOTOGENIN. 



I conclude, therefore, that Dubois's luciferase, a thermolabile sub- 

 stance in luminous cells, is the light-producing body. It gives light in 

 contact with many substances not necessarily oxidizable and an espe- 

 cially bright light with a thermostabile substance (Dubois's luciferin) 

 found in high concentration throughout the body of Cypridina hilgen- 

 dorfii and in small concentration in the blood or juices of other non- 

 luminous invertebrates. I therefore propose the new names photogenin 

 (light-producer, from <pcos, light, and yevvau, produce) for luciferase and 

 photophelein (light-assister, from (poos, light, and w^eXeco, assist), for 

 luciferin. 



As we shall see later (p. 189), the photophelein can not be regarded 

 as an enzyme, because it is used up in the reaction and will not give 

 light with an indefinite amount of photogenin. The photogenin corre- 

 sponds much more to an enzyme, but it is also slowly used up. At 

 present we can only speak of photophelein as a definite substance 

 causing in some way the emission of light from photogenin. 



Perhaps the comparison of the important facts concerning light- 

 production in Pholas and Cypridina shown in table 1 will make clearer 

 Dubois's and my own views, and bring out the contradictory properties 



