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COLOUR AND PHOSPHORESGENCE
185
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result—possibly a quite incidental one——and not the
.
cause
of the
colour
produced.
It is
highly probable,
though it has
to be denitely proved in all cases, that
the pigments of animals are not produced by themselves
but‘ are manufactured from vegetable substances Which
they eat.
The exact course which this manufacturing
process may take and so the colour of the resultant pigment,
appears to depend on the intensity of light.
According to
one theory feéble light is sufcient for the production of
'
red pigment which may be converted into yellow or white
,
pigment under the inuence of light and perhaps other
.
..
inuences.
Blue pigment is also produCed from red when
‘
light is present but is also destroyed by light», so that
blue animals are only maintained that colour because the —
production” of pigment keeps pace with its destruction.
But we have little denite knowledge on this most,important
—
subject which presents problems for the solutionof which
the
combined efforts of biologist and chémist will be
necessary. —
,
.
.
PHOSPHORESCENCE
'
Although many land animals, such as the glow—worm
.
and rey, are able to produce light so that they glow at
night, this power of phosphoresce‘nce, or “ bio—lumines—"_
cence ”
as it- is better called to distinguish it from light
'
produced by the mineral phosphorus, is‘very much more
widespread amongst marine animals.
So common is it
.
that ithas aroused interest from the earliest times and many
_
theories have been advanced-in the attempt to explain the
mystery of its production. For instance the explorer
Franklin thought that phosphorescence in“the sea was due
'
to friction'betWeen the salts pr”ôducing tiny electric, Sparks;
This and other Views are now of merely historic interest
for, though the power
bio—luminescence is possessed by
.