190 Papers from the Department of Marine Biology. 



determine whether a small concentration of photogenin can use up a 

 large concentration of photophelein, providing a sufficiently long time 

 is allowed. We can not use this method, because photophelein decom- 

 poses spontaneously. 



Another way is to determine if a small amount of photogenin can 

 decompose successively added amounts of photophelein without itself 

 undergoing diminution. This method is not unequivocal, since many 

 true enzymes are paralyzed or destroyed by the decomposition prod- 

 ucts of the reaction which they accelerate. 



It was found that if w^e add to 1 c.c. of a weak (1 Cypridina to 50 c.c.) 

 solution of photogenin, successive 1 c.c. additions of a concentrated 

 (1 Cypridina to 2 c.c.) solution of photophelein as soon as the light from 

 the preceding addition has disappeared, after four 1 c.c. additions no 

 more light will appear. The photogenin is therefore used up and can 

 not oxidize additional photophelein, although there is plenty of photo- 

 phelein present, as may be shown by adding fresh photogenin, when a 

 good light appears. With each successive addition of concentrated 

 photophelein, the light, which at first is very bright and lasts about an 

 hour, becomes less brilliant and lasts a shorter time. This is not due 

 to mere dilution of the dilute photogenin, as we can dilute the dilute 

 photogenin to the same volume with water and then upon the addition 

 of photophelein a good light results. We can conclude only that, 

 although photogenin can use up a large amount of photophelein, it 

 is itself changed in some way in the reaction and disappears. We can 

 not say how much photophelein will combine with a definite quantity 

 of photogenin, because we do not know the absolute amount of these 

 substances in a single Cypridina. In the above experiment we added 

 a concentration of photophelein from one Cypridina 100 times {i. e., 

 four additions each 25 times more concentrated) that of the photogenin 

 from one Cypridina. 



Although the evidence goes to show that the photogenin is used up, 

 it is not nearly so rapidly used up as is the oxidase of potato in the 

 production of light from pyrogallol (see p. 231). We must remember 

 also that certain enzymes, as zymase (thermolabile and non-dialyzable), 

 are only active in presence of a coenzyme which is not destroyed by 

 heat and is easily dialyzable. In fact, the photogenin-photophelein 

 system resembles to a very remarkable degree the zymase-cozymase 

 system. There is the same quantitative relation between zymase and 

 cozymase as between photogenin and photophelein. If zymase is 

 present in excess, the coenzyme is all used up ; if cozymase is in excess 

 then the zymase is used up (i7). Nevertheless, however much photo- 

 genin resembles cozymase, I have for the present deemed it best to 

 avoid the termination ase. In absence of more definite knowledge we 

 may provisionally regard photogenin as a substance auto-oxidizable 

 only in presence of photophelein. 



