180 



Papers from the Department of Marine Biology. 



similarity to the disappearance of photophelein in the presence of 

 photogenin, with this exception, that no light is produced.) The 

 experiment seems to indicate a third substance destroyed by heat, 

 in non-luminous parts, which oxidizes (since oxygen is necessary) the 

 photophelein. 



In the extract of the non-luminous species, there is also a similar 

 substance (photophelein) which will give light with photogenin. Unlike 

 the photophelein from the non-luminous part of Cypridina hilgendorfii, 

 it occurs in very small concentration, so that we must use concentrated 1 

 photogenin and concentrated extract of Cypridina x. 



TABLE 2. 



The photophelein from Cypridina x is also destroyed or disappears 

 if the extract stands 1% hours in contact with oxygen, but not in the 

 absence of oxygen. Boiling makes the extract more stable. 



In some other non-luminous forms, widely different in relationship 

 from Cypridina, there are substances which give light with concen- 

 trated photogenin and others which will not, whether the extract has 

 been boiled or left unboiled. The extracts were boiled in order to 

 destroy substances which in turn might quickly destroy photophelein. 



Among the light-giving extracts may be mentioned those listed in 

 table 2. 



Of these forms, Lepas and Chiton gave the best light and of these 

 two only Lepas gave light with dilute Cypridina photogenin. Too 

 much stress must not be laid upon comparative results, because much 

 depends upon the concentration and it is not easy to obtain extracts 

 of comparative concentration. 



'By concentrated photogenin is meant an extract of 1 Cypridina in 0.5 to 1.0 c.c. water. 



