377 
Luminescence of Deep-sea Fishes 
Haneda 
and that the difficulty in seeing it was due to 
the expansion of the chromatophores in the 
transparent, scaleless skin which covers the 
outside of the aperture. When these chroma- 
tophores expand they shut off the light and 
when they contract the light is transmitted 
and can be seen. Possibly the expansion and 
contraction may be determined by the water 
temperature, the degree of darkness or light, 
or by other factors, but I did not determine 
the effects of these factors upon the func- 
tioning of the chromatophores. 
However, from my observations I am of 
the opinion that when these fishes are swim- 
ming in natural conditions at the bottom of 
the sea they are normally luminous, emitting 
light through these ventral apertures. 
I have never been able to observe any 
macrourid fish in a natural condition since 
they are all deep-sea fish and cannot be kept in 
an aquarium. I have been able to examine only 
dead and living material freshly caught by 
trawlers from deep water. When examining 
this freshly caught material I could see the 
luminosity of some, but not of others. When 
the glands were cut open, however, they were 
always luminous. 
The luminosity of young Coelorhynchus 
parallelm may be seen as a beautiful green 
filiform line on the ventral surface. Coelo- 
rhynchus hubhsi has two luminous spots on the 
ventral surface, and I am of the opinion that 
these fishes, when in their natural conditions, 
normally display their luminosity. 
I cannot agree with the opinion that these 
fishes, through the opening of the canal in 
the anal region, discharge a luminous cloud 
into the surrounding sea water. 
CONTENTS OF THE LUMINOUS DUCTS 
Emulsions of the contents of the ducts were 
made in sterile sea water and were examined in 
the dark. 
When first made, the emulsion was uni- 
formly luminous. After standing in vertical 
tubes and settling for 20 minutes, the lumi- 
nosity had collected as an upper layer. When 
shaken up, it was again uniformly distributed 
in the tube. If it was centrifuged, the lumi- 
nosity was concentrated in the sediment at the 
bottom of the tube and the fluid above was 
clear and not luminous. If this precipitate was 
well mixed with sterile sea water the whole 
mixture became uniformly luminous, but if 
it was mixed with sterile distilled water, it 
failed to show any luminosity. 
Changes of temperature showed the fol- 
lowing results. Luminosity was greatest be- 
tween 15 and 23°C. and this is the optimum 
temperature; at 0° C. it ceased; at 3-4° C. it 
was very weak; at temperatures between 23° 
and 45° C. it decreased; above this point it 
finally ceased and could not be reactivated 
when cooled again to 15-23° C. 
The reactions were those of luminous bac- 
teria and an examination under the micro- 
scope showed bacteria and segments of the 
gland duct cells. The bacteria stained red with 
Ziehl’s solution and I was able to culture 
them by the usual bacteriological methods. 
Samples were taken from the organs of every 
fish studied. The characteristics of the lumi- 
nous bacteria from the luminous ducts of 
many species of fishes of the Gadidae and the 
Macrouridae were investigated by the usual 
methods of culture in artificial media. 
I was able to obtain 10 strains of luminous 
bacteria from each of these hsh^s—Lotella 
phycis, Malacocephalus laevis, Hymenocephalus 
gracilis; 20 strains of luminous bacteria from 
Coelorhynchus kishinouyei and Nezumia con- 
dylura; and 14 strains from the other species. 
These strains of bacteria were taken from 
various species of fish taken at different times 
and in different localities. All had the same 
general biological characters but the optimum 
temperature, that is, the temperature at which 
the luminosity was greatest, varied. In some 
cases it was higher than others, but it never 
varied much. The optimum temperature for 
luminosity was lower for the bacteria of those 
fishes which live in deep and therefore colder 
water than for those living in the shallower 
and warmer water. A more complete discus- 
