192 Papers from the Department of Marine Biology. 



a non-luminous species of Cypridina a photophelein occurs in small 

 quantity with properties similar to that in Cypridina hilgendorfii. 



11. Photophelein occurs in extracts (both boiled and unboiled) of 

 many non-luminous organisms, in greatest quantity in Lepas anatifera. 

 The photophelein of Lepas anatifera does not disappear on standing. 



12. Pure protein solutions (peptone, Na nucleoproteinate, albumen, 

 etc.) or dried mammalian blood do not contain photophelein, but urine 

 contains a similar body. 



13. While photogenin will give light with many substances known 

 and unknown, photophelein will give light only with the photogenin 

 of luminous organs. 



14. Cypridina photogenin will give no brighter light with extracts 

 (photophelein) of other luminous forms (Luciola, Cavernularia, Nocti- 

 luca) than with extracts of non-luminous forms, and Luciola photo- 

 genin will not give so bright a light with Cypridina photophelein as 

 with boiled extracts of non-luminous insects. We must conclude that 

 the two substances are not specific for luminous forms, although there 

 is a certain amount of specificity, for photogenin gives the best light 

 with photophelein from the same species. 



15. Bright light can be formed by Cypridina at C. Photogenin 

 is destroyed above 70, the temperature and time depending on the 

 concentration; photophelein only after several minutes' boiling, the 

 time depending also on the concentration. The natural luminous 

 secretion ceases to light at 52 to 54, but the light returns on cooling. 



16. Photophelein is relatively unstabile and disappears on standing, 

 the time depending on the concentration. Photogenin is much more 

 stabile, but also disappears slowly. 



17. The spontaneous decomposition of photophelein is retarded 

 (perhaps prevented) by lack of oxygen, but hastened by addition of 

 preservatives (chloroform, ether, benzol, thymol). Photogenin can 

 be kept longer by addition of preservatives. One sample preserved 

 with chloroform retained its power to give light with photophelein for 

 over 56 days at room temperature. 



18. Saturation with ether, chloroform, benzol, thymol, or chloretone 

 does not affect the light from a mixture of photogenin and photo- 

 phelein. Saturation with butyl alcohol or 20 per cent ethyl aclohol 

 or 16 per cent acetone extinguishes the light, and if the mixture is 

 diluted with water the light reappears. This phenomenon of anes- 

 thesia of a solution is given by photogenin filtered through porous 

 porcelain plus photophelein and difficultly soluble butyl alcohol, so 

 that it can not be due to the presence of cell fragments or to insolu- 

 bility in the 20 per cent ethyl alcohol. 



19. Picric acid, tannic acid, and phosphotungstic acid extinguish 

 the light in very weak concentrations, and the light returns in the case 

 of picric acid if the solution is diluted with water. In the case of 



