On the Phosphorescence of Marine Invertebrata. 75 
and the other only on opposite sides. With a lens of 10 to 12 di- 
ameters, we find that the light often appears successively on dif- 
ferent parts of the body. There is hence no circumscribed phos- 
phorescent organ, as in the Lampyri, Elaters, and Pyrosomas.* 
. The light is due to an infinite number of minute scintilla- 
tions.—T he preceding figure of a part of a Noctiluca much magni- 
fied, represents the actual character of the phosphorescence. ‘There 
isan immense number of points of light. With a lens of 20 to 30 
diameters, the light is like an undefined nebula; but with a lens 
of 60 diameters, it is partially resolved, and with 150 diameters, 
Wholly, into its constituent spangles. Each luminous spot on the 
body is found to consist of a cluster of minute instantaneous scin- 
ullations, dense at the centre, and more scattered towards the cir- 
cumference of the spot. Thus the same phenomena take place 
in the Noctilucze as were observed by M. de Quatrefages in the 
Ophiure and Annelida. Each spot of light is resolvable into con- 
Stituent points, and consists of evanescent scintillations. 
8. The light from the dead Noctiluce or from fragments of 
them, is identical with that from the vigorous living animal.— 
hen the light of the Noctiluce, after frequent excitement, be- 
comes white, it is also more fixed, and finally covers the whole 
body. From numerous experiments, M. de Quatrefages concludes, 
that this kind of light is evidence of disease, or of a decline of 
vigor, and when the light is universal, of death. Microscopic 
examinations make it apparent that in these cases the light is still 
made up of minute points, and it is evidently of the same nature 
with the light given out in active life. 
_9. Precautions necessary to succeed in the preceding observa- 
tions—T he animals should be examined without the use of a 
* The Noctiluca has a depres- 
S100 on one side, and near the 
middle of this depression is the 
Popa ~ same place there 
veable a nh e as 
Jong as half the qepenaage the 
e€ ly is perfectly 
meral en- 
ranulous interior. 
