14 
PACIFIC SCIENCE, Vol. VI, January, 1952 
refj^ 
Fig. 1. Longitudinal section of the luminous organ 
of Polyipnus stereope. phot, Luminous body; refli, refl 2 , 
reflectors; lens, lens; fil, color filter; chr, pigmented 
membrane. 
seeds in a round seed capsule. When fresh 
material is cut with a thin knife, this organ 
appears to be milky blue and shows a bluish 
luminescence. This luminescence may con- 
tinue for 4 to 5 hours after death. Sections 
cut from this organ stain well with haema- 
toxylin. 
Reflector 
This consists of two parts. Part one 
(labeled refl.i in Fig. 1) covers the inside of 
the luminous body and the filter. It is a 
silvery, opaque membrane. Part two (refl.2) 
covers the back of the lens and is composed 
of an arrangement of parallel fibers. Both 
parts reflect light extremely well. 
Light Filter 
Between the luminous body and the lens 
there is a transparent, single component 
which is beautifully colored. In Polyipnus and 
Argyropelecus it is a reddish violet. In Yarrella 
it is a ruby red. The color in some deep-sea 
luminous fishes is reproduced in ”The 
Oceanic Fishes and Flat Fishes Collected in 
1925-1927” by J. R. Norman (1930). Argyro- 
pelecus is shown as a reddish-violet color and 
Bathytroctes rostratus as orange. Photichthys 
argentius has a beautiful green color. 
The tissues of this component are arranged 
in parallel, and its cells contain round nuclei 
and small granules. It may sometimes func- 
tion as a lens, but it should be noted that 
both the curved upper and lower surfaces are 
parallel, the curves being in the same direc- 
tion. Some investigators consider this com- 
ponent as the lens, but in my opinion it is 
simply a color filter. 
These luminous organs in situ, when viewed 
ventrally by daylight, display a beautifully 
colored light in fresh specimens, but, if 
viewed laterally by daylight, this coloration 
can be seen localized only in this filter com- 
ponent and nowhere else. 
I have examined living Polyipnus stereope in 
the dark, and have found the luminescence, 
as emitted, to be a greenish blue, whereas the 
color of the filter is violet. I was unable to 
obtain any living Yarrella, and am therefore 
unable to compare it with Polyipnus. The two 
species have filters of different color. One is 
violet and the other ruby red, and perhaps 
the color of their luminescence may be due 
to this difference in the color of their filters. 
However, owing to a lack of material for 
comparative purposes, I am unable to make 
any positive statement on this point. 
Lens 
The lens is a perfectly transparent, gelatin- 
like substance, and many investigators de- 
