212 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
organ designed for the support of luminous bacteria. The organ is 
large, just under the eye, and the bacteria are of a special kind which 
will not grow on ordinary culture media or on the outside of the fish. 
They are spoken of as symbiotic luminous bacteria and present only 
another case of a mutual benefit partnership between two different 
organisms. The fish have the benefit of the light while the bacteria 
are supplied with free board and lodging. A very rich system of 
blood capillaries brings food and oxygen so necessary for the lumi- 
nescence of these bacteria. It is characteristic of luminous bacteria 
that their light is shining day and night continually, as long as 
they are alive, while other luminous forms only light when they are 
stimulated. We observe this in the phosphorescence of the sea, 
which only occurs when the water is agitated by wind or the ship’s 
propeller or movement of oars. Consequently these fish have had to 
develop a screen to cut off the light, and we find a fold of black 
pigmented skin, like an eyelid, that can be drawn up over the lumi- 
nous organ and so obscure its light. Hence the name of the fish, 
Photoblepharon, or “ light eyelid.” The fishermen of Banda cut off 
these luminous organs, remove the screen, and impale them on hooks 
for bait. The light will shine steadily for a night’s fishing. But 
Photoblepharon itself swims about in the sea turning its great lumi- 
nous organ on and off like many another fish that manufactures its 
own light material without relying on the kind assistance of lumi- 
nous bacteria. Only a careful microscopic examination reveals the 
true nature of the luminescence of Photoblepharon. 
One can not be too careful in investigating the light production 
of a new form. I remember once while collecting luminous beetles 
in Cuba I was astonished to find a luminous frog. As fish are the 
highest creatures which can produce light, a frog with luminous 
organs would be a rare find indeed. My hopes were short-lived, 
however, for closer examination revealed that the animal had just 
finished a hearty meal of fireflies, whose light was shining through 
the belly with considerable intensity. 
Some cases of luminosity are on record in connection with man 
himself. Before the days of aseptic and antiseptic surgery, wounds 
frequently became infected with luminous bacteria and glowed at 
night. The surgeons of that time believed that luminous wounds 
were more apt to heal properly than nonluminous ones. Perhaps 
there is some truth in this view. Luminous bacteria are harmless 
nonpathogenic forms and it is possible that such forms might crowd 
out pathogenic bacteria striving to gain the ascendency on the 
wound. 
In the older literature there is a case of luminous sweat and several 
cases of human urine, luminous when voided. If these observations 
are really true, and so far as I know they have not been confirmed 
