FACTS AND THOUGHTS ABOUT LIGHT-EMITTING ANIMALS. 231 
the Alcyonarian Pennatulidse and Grorgonidse compensates for 
the comparative absence of the phenomena in the other members 
of their group. Even in the cold North Sea, the Sea-pens, 
and their long-stalked, short-polyped allies, the Virgularice , add 
to the sea light, and the Gorgonice do the same. They are re- 
splendent in the Mediterranean ; and Moseley states that all the 
Alcyonarians dredged up by the Challenger from deep water 
were found to be brilliantly light-emitting, and that their phos- 
phorescence agreed in its manner of exhibition with that ob- 
served in shallow-water forms. He examined the light emitted 
by three species of deep-sea Alcyonaria with the spectroscope, 
and found it to consist of the red, yellow, and green rays only. 
Panceri notices the light of Pennatula jphosjphorea , which 
is an eight-tentacled Alcyonarian, with a stem with pinnate 
branches, carrying zooids or polypes. The long stem reach- 
ing below the branches consists of canal tubes, which are 
in communication with the polypes through the branches ; 
and it is covered with sarcode that is comparatively rudi- 
mentary, and which is liable to become infiltrated with water*, 
or to be hydropic, when brought up' from the deep sea. The 
polypes, when fully expanded, are in rows on the upper surface 
of the branches, and each has eight pinnate tentacles, and at 
their base a slight swelling on the outside. From each of these 
eight swellings an opaque white cord passes down the outside of 
the visceral cavity of each polype to the sarcode of the branch. 
These cords are canals in the sarcode, and when they are 
compressed, their contents may pass either into the hollow of 
each tentacle, or backwards into the tubular cavities of the 
branchlets and stem, and very little force suffices to burst 
them. When examined under the microscope, the contents 
are found to be cells and a fluid, and the opacity and 
white colour are produced by the cell contents, which consist of 
minute highly refracting globular particles, having, chemically 
and optically, all the properties of fatty matter. This substance 
is remarkable for its persistence without undergoing decompo- 
sition long after the death of the polype. In the substance of 
the cords there are cells which are stellate in shape, with pro- 
longations, and resembling multipolar ganglion nerve cells ; and 
others are simple enlargements along the course of a fibre. Be- 
sides these there are many albuminoid granules and some white 
particles of a mineral nature, but which does not consist of 
carbonate or phosphate of lime. 
Now this Sea-pen is luminous universally, when seen under 
favourable circumstances in the open sea, and it has its hours 
of darkness. When caught to be experimented upon, the 
animal lights up in a very remarkable and definite manner. 
Should the long supporting axial stem be pinched, the polypes 
