FURTHER STUDIES ON THE CHEMISTRY OF LIGHT 
PRODUCTION IN LUMINOUS ORGANISMS. 
By E. Newton Harvey. 
The results embodied in this paper are the outcome of experiments 
made upon the dried luminous organs of a small ostracod crustacean, 
Cypridina hilgendorfii, abundant in the coastal waters of Japan. The 
structure of the luminous cells has been well described by Dahlgren in 
the Journal of the Franklin Institute for June 1916, and by Yatsu 
(Jour. Morph., vol. 29, p. 435, 1917). These cells contain the luminous 
substances concerned in the production of light, which are projected 
into the sea-water as a luminous secretion. This paper deals par- 
ticularly with the chemistry of the luminous reaction. It will be con- 
sidered in two sections, viz: I, reversibility of the photogenic reaction 
in Cypridina. II, the chemical nature of Cypridina luciferin and 
Cypridina luciferase. 
Much of the work was performed in the Zoological Laboratory, Impe- 
rial University, Tokyo, Japan, and it gives me pleasure to acknowledge 
the kindnesses of Professors Ijuma, Yatsu, Watase, and Goto during 
my stay at the university. I am also deeply indebted to Professor 
C. Ishikawa, of the Agricultural College, Tokyo, for much assistance 
in collecting material, and I express my sincere thanks for his interest 
in my work. 
I. REVERSIBILITY OF THE PHOTOGENIC REACTION IN 
CYPRIDINA. 
In a previous paper on the question of animal luminescence! I have 
described two photogenic substances in Cypridina hilgendorfit, which 
I called photogenin and photophelein. Photogenin is destroyed below 
the boiling-point, is non-dialyzable, and is prepared by making a cold- 
water extract of the luminous animal and allowing it to stand in the air 
until no more light appears on shaking. This indicates that one of the 
photogenic substances, photophelein, has disappeared, leaving the 
photogenin. Photophelein is not destroyed by short boiling and will 
dialyze. It is prepared by making a hot-water extract of the luminous 
animal. The hot water destroys the photogenin, leaving the pho- 
tophelein. Whenever two such solutions are mixed light appears. 
On the grounds of method of preparation, relation to temperature, 
and dialysis, I regarded photogenin as comparable to luciferase and 
1Harvey, E. N., Am. J. Physiol., 1917, xlii, 318; also, The Chemistry of Light Production in 
Luminous Organisms, Carnegie Inst. Wash. Pub. No. 251, pp. 171-234, 1917. 
Gt 
