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and Zygodactylce , whose light is decided, although like a dim 
halo sometimes, but grandly golden at others, and especially 
when the creatures are broken by hauling in. Agassiz noticed 
that the blue tint of the seeming phosphorescence, was often due 
to a Medusa, Dysmorphosa fulgurans , which breeds others 
from its proboscis, and thus readily adds to its vast numbers. 
On the other hand, the stem or trophosome, out of which Obelia 
is developed, has a pulsating light running up it, whilst the free- 
swimming disc is said to be non-luminous. The globular jelly- 
fish with paddles, or the Ctenophora, so active in the sea, are 
brilliantly luminous, and it appears that many of the horny 
Sertularians give out light. The luminous part of the Medusae 
is superficial when they are swimming and entire, and it appears 
to be restricted to the upper part of the umbrella, to the margin 
of the disc, and to the tentacles. But extreme irritation and 
tearing will develop light apparently everywhere, and the slip- 
pery semi-solid sarcode clings to everything, and is for a while 
luminous. It does not appear that the natural luminosity is 
greater underneath, where Schafer has noticed radiating nerve- 
fibres, than on the top, where there is a delicate epithelium, 
whose flat cells contain minute points of fatty matter, and where 
no nerves have been found. The tentacles get luminous, and they 
are without any evidence of nerve, except perhaps where they 
start from the margin of the umbrella or disc. There is often 
much defined light at the so-called eye-spots at the edge of the 
disc, and it may be in relation to the epithelium there, related 
as this is to nerve. In the mass of the animal there is no highly 
differentiated protoplasm, but there is much of a low character, 
and it is all this that is so golden and white, when rupture has 
taken place. It is hard to believe that the nerves and fatty 
matters have anything to do with the luminous phenomena here, 
and certainly they have not in the trophosome of Obelia. Pro- 
toplasm, in a state of active nutrition, appears to be the seat of 
the movement which produces the light-wave. 
It must be remarked that the great jelly-fish of our coasts 
and of other seas are not luminous during the whole of their 
summer life, for they may be seen crowding many estuaries in 
the hot months, as the twilight merges into night, and not a 
sparkle of light is visible amongst them. 
Phosphorescence does not appear to have been noticed in the 
reef-building corals, nor in those solitary ones which can be 
kept in aquaria, but some of the Actinidse, or sea-anemones, 
are brilliantly luminous. One notable example is the mud- 
loving, free, long-bodied Iluanthos scoticus , which leaves its 
rayed disc just above the surface of the ooze, shining like a star 
here and there, and retaining its light when brought up with 
the dredge. The extraordinary luminosity of vast numbers of 
