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lations, closely approximating to one another at the centre of the 
‘'‘'phosphorescent” portions, hut disseminated and clearly distin- 
guishable at the edges. Occasionally there may be seen isolated 
sparks at the extreme limit of the luminous part, or even beyond 
it (fig. 8). In employing very fresh and vigorous examples of 
Noctilucie, I have been enabled myself to inspect and to exhibit 
this phenomenon to M. Bouchard-Chantereaux under a magni- 
fying lens of 240 diameters. 
Thus Ave find in the Noctiluc® the same phenomena which 
we observed in the Annelides and Ophiuridfe. In neither case 
does the spark which presents itself consist of an unbroken body 
of light, but it represents, so to speak, the sum total of an 
infinite number of evanescent scintillations. Each luminous 
manifestation is a nebula, so to speak, resolvable, Avith a suffi- 
ciently high magnifying power, into a cluster, just as we find it 
to be the case in a celestial nebula. But in this instance there 
are no “ fixed stars for even Avhen the luminous point remains 
apparent to the unaided vision for a few moments, and the 
microscope is brought into play, this is not only decomposed in 
space, but is also resolved in time, the component scintillations 
being instantaneous and evanescent ! 
It is quite obvious from the facts thus re\ T ealed, that the lumi- 
nosity of Noctiluefe is a phenomenon very different in character 
from that of phosphorus exposed to the air. No one Avould for 
a moment pretend to say that scintillations such as those exhi- 
bited under the microscope could be the result of a sloir com- 
bustion; and an active combustion (Avhicli is always accom- 
panied by great heat) could not proceed in the very heart of the 
living tissues. Indeed, careful experiments have satisfied me 
that no elevation of temperature takes place even where the 
luminosity of the animalculae is most brilliant ; there has been 
no apparent influence upon the most sensitive thermometer 
when plunged into a mass of these forms all brightly lumi- 
nous, presenting, indeed, the maximum of phosphorescence. 
In the electrical fishes, Ave knoAV that there is a special appa- 
ratus for bringing into play the physical agent, electricity ; in 
the Lampyridee a particular organ secretes the phosphorescent 
matter : Ehrenberg lias described similar luminous organs in 
Photocliaris and Thaumantias, and Meyer in Pyrosoma. 
Nothing of the kind, hoAvever, exists in the 0 phi mid® or 
Annelides Avhicli I have carefully investigated ; nor is it the case, 
as Ave haA T e seen, in theNoctilucie. Here the living organism itself, 
and what maybe termed par excellence the vital tissue, namely, 
the muscular, produces the luminosity solely in virtue of its A T ital 
function, namely, in that of contraction ; and the fight emitted 
appears to be perfectly pure and independent of any other 
product. 
