186 



Papers from the Department of Marine Biology. 



or temperature upon a process at any particular instant, rarely ob- 

 tained in the study of enzyme action or even of cell action, except 

 where some movement is affected. For instance, we can heat pepsin 

 to 60° and then cool it and see if it will digest protein. If we find that 

 it will digest protein, that gives us no information as to a reversible 

 inhibition at 60°, an inhibition which might become non-reversible if 

 we kept the pepsin at 60° long enough to test directly the power of 

 digestion. We can, however, heat photogenin and photophelein to 60°, 

 cool them, and find out immediately if they give light. 



PROTEIN PRECIPITANTS. 



The light disappears in a phosphorescent mixture of photogenin and 

 photophelein when the following substances are added to the concen- 

 trations indicated: tannin — m/2500 to m/5000; phosphotungstic acid — 

 m/2500 to m/5000; picric acid — m/500, assuming a saturated water 

 solution to be 1 .03 per cent or m/22. 



Table 6. — Effect of acids and alkalies on light-production. 



A peculiar phenomenon observed with phosphotungstic and tannic 

 acids but not with picric acid is that, at the lower limit of extinction, 

 the hght reappears after first disappearing and more acid must be added 

 in order to extinguish it again. Care was taken to make sure that the 

 phenomenon was not due to more perfect adaptation of the eyes to the 

 dark. When the light is extinguished by dilute picric acid it will 

 reappear again on dilution with water. 



ACIDS AND ALKALIES. 



The effect of acids (HCl) and alkalies (NaOH) can be seen by adding 

 1 c.c. of the acid (or alkali) of a definite concentration to 1 c.c. of a 

 glowing mixture of photogenin and photophelein. The concentration 

 of the acid or alkali in the mixture will thus be one-half of the concen- 

 tration added. The results are given in table 6. 



The effect of acid (HCl) and alkali (NaOH) was also studied in the 

 following way: 1 c.c. fairly dilute (1 Cypridina to 10 c.c.) photophelein 

 was mixed with 1 c.c. n/500 HCl, allowed to stand 1 hour and then 



