PHOSPHORESCENCE. 78 
may be the cause of the light. It may be regarded as certain that 
there is no obvious warmth accompanying the light; on the other 
hand, it might require an instrument as delicate as Professor 
C. V. Boys’ Radio-micrometer to definitely settle the matter. 
(This instrument is capable of shewing the heat from a lighted 
candle more than a mile away). Sir Oliver Lodge says that if we 
could discover the Glow-worm’s secret of converting some unknown 
source of energy into light we should be able to produce light 
without heat. As an additional fact, there is no doubt that the 
Glow-worm has a direct control over the light it emits: it can 
switch it on or off, so to speak, at will.” 
We may now turn to the strikingly beautiful phenomenon 
known as Marine phosphorescence—beautiful in all its degrees, 
from the richly illuminated ocean under tropical skies to the multi- 
tudinous little flashes of light which show in the mill race of water 
leaving the paddles of a Channel steamboat. Even on our own 
coasts marine phosphorescence may be seen in great beauty in a 
continuously warm summer (an occurrence which seems pretty rare 
now), when the temperature of the water is probably much more 
congenial to the habits of the small organism by which the phenom- 
enon is usually caused. In former years I have seen it to great 
advantage at Lowestoft, more particularly in the harbour. By day 
it formed a pink-buff-coloured scum on the quiet surface of the 
water, but at night this scum gave a lovely display of phosphorescence 
if a handful of sand or small pebbles were thrown into it, or a rope 
jerked into undulations across the harbour, or a boat were rowed in 
through it. The organism concerned in this was Nocrinuca 
MILIARIS, and specimens collected in a bottle phosphoresced for 
some hours afterwards on shaking. 
NocrrLvuca MILIARIS is a very small organism, being practically 
microscopic. It is shaped almost exactly like a peach, with a cilium 
or tentacle where the stalk would be. It multiplies by self-division, 
