373 
Luminescence of Deep-sea Fishes — Haneda 
trifossa, Nezumia, Grenurus, Trachonurus, and 
Coelorhynchus as a lens-shaped body, or scale- 
less "fossa” or naked area. 
I have collected and studied the compara- 
tive structures of the luminous organs of 
many specimens of various species, and I 
have also cultivated their bacteria in artificial 
media. The results of these observations are 
presented here. 
! Acknowledgment: I wish to express my sin- 
cere gratitude to Dr. Pletsch, Scientific and 
Technical Division, ESS, GHQ, SCAP, who 
! helped me in gaining publication of this 
„ paper. 
I MATERIAL 
I Altogether I have examined material from 
I two species of the Gadidae and 14 species of 
! the Macrouridae. 
\ The Gadidae are comparatively shallow- 
1 water fish. They may be caught close to the 
' coast of Japan. Physiculus japonicus occurs in 
j water varying in depth from 30 to 50 fathoms. 
Lotella phycis is sometimes taken in extremely 
shallow water near the surface. This enables 
I one to keep them in an aquarium tank where 
each can be observed in a natural state. They 
may be caught at any time of the year by 
hook and line, and their luminosity may be 
seen if they are taken during the darkness of 
the night, 'Physiculus japonicus is occasionally 
taken by trawlers. 
The Macrouridae are always caught by 
trawlers since they are deep-water fishes living 
in over 100 fathoms of water. They are taken 
most abundantly during the winter in Japan. 
STRUCTURE OF LUMINOUS ORGANS 
Studies made up to the present time show 
that the Gadidae and Macrouridae possess 
the same open type of luminous organs. 
These organs may consist of the following 
four components: (a) A luminous gland; (b) 
its canals and their openings; (c) lenses with 
an external ventral aperture covered with a 
thin transparent skin through which light is 
transmitted; and (d) a reflector and chroma- 
tophores. 
In some species the luminous gland may 
be so small as to be almost invisible. The 
canal leading from the gland may be either 
very short or very long. The structure of the 
lens may be very complicated, or very simple 
and inefficient. The reflector may vary also in 
its efficiency according to its structure. 
The external ventral aperture through 
which light is transmitted is visible externally 
and may be comparatively large, or very 
small, or it may be absent. It may be bean- 
shaped, or circular, or very long and filiform, 
and in some species there may be two ex- 
ternal apertures. The figures illustrate the 
many forms which can be seen. In the first 
type the luminous organ is very small and 
barely visible (as in Coelorhynchus anatirostris) . 
It has a very short luminous duct, and is 
situated very close to the anus lying ven- 
trally in the muscles, and has neither reflector, 
lens, nor external aperture. The organ cannot 
be seen externally, and gives the impression 
that it does not exist. Only when the fish is 
sectioned longitudinally and a cut is made 
through the organ can it be seen that there 
is a luminous duct which is extremely small 
and inefficient. In this duct are luminous 
bacteria. Although it is vestigial, it is never- 
theless a true luminous organ, difficult as it 
is to determine. 
Coryphenoides garmani and C. misakius are 
two other species which have very short and 
inefficient luminous ducts. The lenses and 
external apertures are inefficient, and from a 
casual inspection it is difficult to say whether 
they are luminous or not. However, luminous 
bacteria live in the duct of the gland. 
In what may be considered the normal type 
or the typical luminous organ — such as that 
found in Physiculus japonicus, Lotella phycis, 
Ahyssicola macrochir, Coelorhynchus kishinouyei, 
Coelorhynchus japonicus, and Nezumia condylura 
— the organ consists of a rather large lumi- 
nous gland, the reflector, the lenses, and a 
scaleless external aperture covered with thin 
transparent skin. The canal in some species 
is rather long and in others very short; for 
