THE PHOSPHORESCENCE OP THE SEA. 29] 
now we must call to mind tlie fact, that amongst the most 
characteristic properties of “ sarcode,” we find what may he 
designated an indefinite contractility. Such is the entire con- 
stitution of the inner substance of the Noctilucae, in which no 
other distinct organization is visible ; and we shall now proceed 
to impure into the nature of the “ phosphorescence” produced by 
animalcube so remarkable for the simplicity of their structure. 
First, it is easy to recognize beyond all doubt, that the emis- 
sion of light takes place independently of all contact with the 
atmosphere ; and that it is not influenced by the nature of the 
gas with which they are brought into relation, provided it does 
not cause sudden death. 
The first statement may be easily verified by collecting a 
colony of Noctilucac in a glass tube, so that they form a layer 
of 10 to 12 centimetres (about 4 inches) in thickness. It will 
then be found that the column is equally luminous through- 
out its whole extent, notwithstanding that the uppermost por- 
tion rises almost above the surface, whilst the remainder is 
deeply submerged. If we go so far as to place the Noctilucte 
in as perfect a vacuum as can be obtained, we find that, far from 
losing their luminous property, they shine with a continued 
brilliancy till life becomes extinct ; but then the attempt to 
excite their luminosity, even by the admission of oxygen gas 
in place of atmospheric air, is quite futile : it has disappeared 
for ever. Finally, if Noctilucoe be placed in inverted tubes, and 
if we introduce severally into these tubes, atmospheric air, 
oxygen, hydrogen, nitrogen, and carbonic acid gas, the results 
will be found to be alike in each, neither description of gas 
affecting the luminosity in a manner different from the rest. 
These experiments suffice to prove that the light emitted by 
Noctilucm is certainly not the result of combustion ; and the 
following serve to show that it is independent of any external 
secretion. 
We have already stated that luminous water passed through 
linen is quite dark after filtration, leaving the luminous ani- 
malcule upon the filtering material. 
The same result follows if, instead of water, we employ milk — 
a fluid which becomes so readily charged with the luminous 
mucus of the Medusae. 
Again, if Noctiluce be placed in ether, it remains perfectly 
obscure ; the animalcuke forming a luminous sediment at the 
bottom of the tube. Again, if the hands or any object be 
rubbed with the Noctilucae remaining upon a filter, it some- 
times happens that luminous traces are the result. These one 
might be led to attribute to some luminous secretion, either 
internal or external ; but a nearer examination with the lens 
leaves no doubt that these traces are due to fragments which 
no. hi. x 
