The Chemistry of Light-Production in Luminous Organisms. 183 



DIALYSIS. 



Photophelein will dialyze through heavy parchment and collodion 

 fairly readily, in the case of collodion sometimes appearing in the dialy- 

 sate in the course of 2 hours. 



Photogenin dialyzes with difficulty and with some collodion tubes 

 not after a period of 36 hours. In others a very slight amount will 

 pass in that time and in one experiment with heavy parchment paper 

 a very shght dialysis occurred in 12 hours, but usually there was none. 

 The collodion tubes and the paper did not leak in any of the experi- 

 ments recorded. 



ADSORPTION. 



Both photophelein and photogenin are removed from solution by 

 washed boneblack and washed freshly precipitated Fe(0H)3. To serve 

 as control the last washings from boneblack and Fe(0H)3 were added 

 to photogenin and photophelein and tested with photophelein and 

 photogenin, respectively, to make sure that the adsorption was not 

 apparent and due to destruction by foreign substances from the adsorb- 

 ing media. 



TEMPERATURE. 



Lund (3) finds that in Cypridina squamosa (?) and Cyclopina gracilis 

 the fight from the luminous secretion disappears at 50° and if heated 

 above 50° (as high as 70° but not above) it will again reappear at 50°. 

 The time factor is always involved in determining the critical points in 

 the effects of temperature, and I find that the concentration of the 

 light-producing substances is also involved. Therefore the exact tem- 

 perature of destruction of photephelein and photogenin depends upon 

 their concentration and the time of heating. I find that cypridinas 

 dried over CaCl2, ground, and the powder suspended in sea-water give 

 a beautiful fight which disappears when heated to 56°, but returns on 

 cooling. If heated to 65° and cooled, the fight also returns, but does 

 not return if heated to 70° and then cooled. A very concentrated 

 mixture of photogenin and photophelein may be heated above 70° and 

 whole cypridinas heated to boiling wiU occasionally give a faint light 

 when cooled. The fight from the normal secretion of Cypridina dis- 

 appears at 52° to 54°, and returns on cooling, so that we may regard this 

 as the inhibition temperature and something above 70°, depending on 

 the concentration, as the destruction temperature. These results are 

 in good agreement with those of Lund. 



The time necessary to destroy photophelein at 100° depends also 

 upon its concentration. In dilute solution (1 Cypridina to 25 or 50 c.c. 

 water) boifing for 1 minute is sufficient, but in concentrated solution 

 (1 Cypridina to 1 c.c. water) 5 minutes' boiling is necessary. 



In Pholas dactylus (5) photophelein (luciferin) is destroyed above 70°, 

 whereas in the firefly (both Photuris and Luciola) it may be boiled for 

 10 minutes without destruction. 



