298
THE BIOLOGY OF FISHES
Not many shes, however,.take to this mode of life;
_
as a rule, they are the suerers from all kinds of external
and internal parasites (Crustacea and worms). But a
remarkable instance of what seems to befriendly parasitism
was
discovered by Max Weber on
Siboga Expedition
to the East Indies. In freshwater ponds or craters he found
shes (Anomalops and Photoblepharon) with
what appeared to be a luminous organ under the eye, This
organ was later examined by Buchner, who has shown that
it is composed of a compact mass of bacteria,œ From this
discovery, as already mentioned, Buchner has come» to. the
conclusion that all the luminescent organs in shes have
developed under the inuence of bacteria, these being the
actual source ofthel_uminescence (1924),
_.
,
_
It“ has -1been supposed by
that theSe luminous
organs were of some special use to their
as attracting— friends and: food—or? Warning -eemies, ahd“s'0 0111
These small shes, however, Swim about in shällowçw—atef,
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and Steche (Brehm’s T ierleben) found that the light was
“
burning
”
during the day as well as the night. Once he
came upon quite a colony of them and compares their illumi—. '
nation to a number of small electric lamps, which faintly lit
up the coral blocks among which the shes live, 'But the
,
shes are able to turn out the light by rotating the whole
organ inwards’ as well asby pulling up an outer: fold of skin
like a shutter.
Steche “thinksthat in this way the shes areable to attract the small : planktoh-aanimab, 1ike—shtimps,
'
'Which, are attraeted by light, As -most shes'_managepto
capture.Ïthes‘e without any lights, this explànati0nrseems a
little . strained'; .:
no explanation_ is needed; ‘ The
of}Banda(l\/lalay)_,vvhere
sheslive, make
good use of ’theÿphenomenon;
;' they Cut out the
and attaCh‘ itÏto lines just above the. hait '
on
the hooks. With this strange shing apparatus {they
catch the larger sh—whitäh live in deep
outside the
crater—.u
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