THE PHOSPHORESCENCE OE THE SEA. 
283 
If water^ charged with Noctilucse, and which appears uni- 
formly luminous; be poured into a narrow glass; oi'; in pre- 
ference; into a tube seven to eight millimetres in diameter, it 
will at once be perceived that this water is illuminated only in 
isolated places. If the luminous points be examined with a 
pocket lens, the animalculm are easily distinguishable, and it then 
becomes apparent that they alone are phosphorescent, whilst 
the siUTOunding liquid is perfectly obscure. 
After the tube has been allowed to stand for a few minutes, 
the Noctilucas rise to the surface and form a luminous layer, 
below which the water is totally deprived of its phosphores- 
cence. 
In order to restore to the liquid its original appearance, it 
suffices to agitate it slightly, whereby the Noctilucao are once 
more disseminated throughout the whole body of water. 
In the same manner as the naturalists referred to, I have 
subjected luminous water to filtration. (A rather fine hand- 
kerchief suffices for the experiment.) The Noctilucas remained 
upon the linen, to which they imparted a brilliant light ; whilst, 
on the other hand, the filtered liquid presented no signs of 
phosphorescence, notwithstanding every means employed to 
promote it. When the Noctilucae were carefully washed from 
the filter, and placed in water that was previously dark, they 
at once imparted to it a phosphorescent appearance. Without 
entering into further details, I think that these experiments, 
which may be repeated by persons possessing even the most 
limited facilities, serve to show that, notwithstanding any ap- 
pearances to the contrary, the diffused phosphorescence of the 
ocean is due to the presence of these Noctilucae.* 
But, we may be asked, whether we mean to imply that this is the 
sole cause of the phosphorescence. By no means. It may be that, 
as Newland surmises, in some cases, the spawn of certain fishes 
contributes to its manifestation, or perhaps, in certain excep- 
tional cases, it may be due to some extent to the presence of 
animal matter, similar to that which is formed on the surface 
of putrefying fish, and which may become dissolved in the 
water, as suggested by M. Becquerel, so as to communicate to 
it a luminous property. Nevertheless, in the presence of facts 
so clearly established in Europe by several naturalists, and in 
the latitude of the Cape by M. de Tessau, observations of the 
* It follows, as a matter of course, that the Noctilucoe may contribute to 
the manifestation of partial phosphorescence as well, when, as I have often 
seen them, they are greatly disseminated ; and, on the other hand, it has 
happened that in waves presenting the uniform luminosity which I have 
called diffused phosphorescence, I have met with the more brilliant scintilla- 
tions produced by Annelides and Crustaceans mixing their light with that of 
the Noctilucse. 
