Harpodon nehereus — Haneda 
137 
stay by the nets, hoping that with careful 
sorting there might be some living material 
available when the nets were lifted. 
Fortunate’y I was able to secure some, and 
the results will show the significance of dis- 
tinguishing between living material and that 
which may have been the material described 
so often as "newly caught.” 
I examined very carefully a considerable 
amount of dead but fresh material in the 
Singapore Fish Market during November, 
1943, and February, 1944, in order to deter- 
mine whether there were any luminous or- 
gans or luminous spots, but failed to find any. 
In April, 1944, I was able to obtain living 
material by crossing over to Karimon and 
actually staying by the nets which are set in 
the Gelam Straits off Tanjong Balai, Kari- 
mon Island, Rhio Archipelago. 
It is significant that of all the living spec- 
imens I obtained, not a single one displayed 
the slightest luminescence. On the other 
hand, all of the dead specimens were strongly 
luminescent. In some cases the whole body 
was luminous; in others only a part was lumi- 
nous. Moreover, the luminosity in some cases 
was confined to the surface of the whole 
body, while in others it could be seen deep 
inside the body. 
Another interesting observation was that 
the luminosity of Harpodon was much 
brighter than that of the other kinds of fish, 
crustaceans, etc., in the catch, which, inciden- 
tally, were luminous, but to a lesser degree. 
Bacteriological cultures were made from 
both the outside and inside of the bodies of 
this dead luminous material, and subjected to 
the usual bacteriological tests. The results 
indicate that the luminosity of Harpodon, 
when dead, is due simply to luminous sapro- 
phytic bacteria and that it differs in no way 
from that which can be observed in other 
dead fish and other animals taken at the same 
time. 
It must not be overlooked that the flesh of 
Harpodon is almost like jelly, possessing an 
extremely high water content, and is an excel- 
lent medium for the easy invasion and rapid 
development of bacteria, much more so than 
the tough muscular flesh of other fishes and 
Crustacea. 
The rapidity with which bacteria develop 
in tropical countries is well known, and this 
case furnishes an excellent illustration. In 4 
to 5 hours after death the effects of luminous 
bacteria are already visible on the surface of 
the body. After 7 to 8 hours luminosity can 
be seen to have extended to the innermost 
parts of the body. 
It is clear, therefore, that what is meant by 
"newly caught” material should be expressed 
more precisely. More frequently this expres- 
sion means "newly landed” either at the place 
normally used by fishermen for landing their 
catches, or perhaps in the market place, miles 
from where the fish were caught. The primi- 
tive and slow methods of handling and mar- 
keting fish in tropical countries are proverbial 
and there would be ample time for Harpodon 
to become luminous as a result of bacterial 
action even if "newly caught” according to 
tropical standards. 
Luminosity is so associated with deep-sea 
fishes that it seems to be considered a reason- 
able possibility that if a fish is either luminous 
or an inhabitant of the deep sea it is probably 
both, especially if it has any resemblance to 
some well-known form of luminous deep-sea 
fish. 
With its gaping mouth, large teeth, small 
eyes, and soft body, the resemblance of Har- 
podon to some of the Chauliodontidae might 
well encourage the belief that it was a deep- 
sea fish, and that the luminosity seen after 
death was normal during life. This resem- 
blance to a deep-sea form misled even so 
great an authority as Gunther (1880: 584). 
Acknowledgment: I wish to express my 
hearty thanks to Mr. W. Birtwistle, former 
Director of the Fisheries Department of Sin- 
gapore and Federated Malay States, who 
helped me in many ways during my stay in 
