THE PHOSPHORESCENCE OE THE SEA. 287 
of a luminous mucus, which continued to sliine after its 
separation from the animals. 
2. On two occasions only I have found Crustacea, whose 
internal substance emitted such a constant and uniform light, 
that, in the dark, the most minute details of organization were 
clearly distinguishable. No phosphorescent matter exuded 
from the body. 
3. In the great majority of cases I have seen the light 
manifest itself in sparks, or scintillations, along the course of the 
muscles alone ; and only during their contraction. In this case 
there was a production of pure light, independent of material 
secretion. 
It is this last mode of phosphorescence, at once the most 
ordinary and the least to be expected, which has been the 
special subject of my researches. 
My observations were first directed to various species of 
Annelides, belonging chiefly to the genera Polynoe and Syllis, 
and to some of the smaller Ophiuridge, occasionally found in 
such great numbers under stones, and amongst fucus recently 
stranded by the tide.* 
In common with Duges, Ehrenberg, and no doubt many other 
naturalists, I have occasionally seen these Annelides and 
Radiates emit a light sufficiently powerful to strike an eye- 
witness, even without his attention being drawn to the pheno- 
menon, and notwithstanding the illumination of a good lamp. 
The first-named animals more especially presented the appear- 
ance (to use an expression of Ehrenberg) of ignited cords of 
sulphur, — the fight appearing to be uniformly distributed over 
the whole body. 
But when they were examined with the aid of a simple lens, 
this uniform fight was found to resolve itself into a series of 
luminous points placed on either side of the body, and covering 
the spaces occupied by the little wart-like processes which serve 
as the locomotive organs of Annelides. 
The same appearance was presented in the Ophi arid®. Now 
and then the arms (radiating members) appeared to be com- 
pletely incandescent ; but the lens revealed upon each of them 
a series of luminous specks, alternating with intervals of dark- 
ness. The body itself is never luminous, and these phenomena are 
only observable when the animal is in motion. The Annelide 
must be progressing, or the Ophiura moving its limbs to and 
fro, before the fight becomes perceptible in the surrounding 
obscurity. As soon as either assumes an attitude of rest, the 
* I regret that I did not determine the various species which formed the 
subjects of my investigations. Absorbed with the study of the phenomenon 
itself, I was unable to devote to the zoological inquiry the attention which it 
deserved. 
