SPONGES AND ANIMALCULES 
369 
countless myriads upon the upper stratum 
of the water on calm summer nights that is 
especially due the diffused form of phosphor- 
escence which is more essentially characteristic 
of temperate latitudes. Under the most favour- 
able of these conditions, the waves falling upon 
the strand leave as they retreat a glittering 
carpet of scintillating points ; the oars of the 
passing boat seem as it were to dip into molten 
silver; while on the high seas the revolving 
screw or paddle of the steam-vessel leaves in its 
wake a broad, luminous track as far as the eye 
can reach. A glassful of water taken from the 
sea at such times immediately reveals the origin 
of these wonderful phenomena. Here and there 
will be seen floating minute bladder-like trans- 
parent spheres, resembling as nearly as possible 
small granules of boiled sago. Investigated more 
closely with the microscope, each individual 
speck will be found to exhibit a pouch-like 
contour, having a central furrow, from which the 
lash projects, and upon which the minute mouth- 
aperture opens. Irritated by agitation in any shape or form, the Noctilucas at once respond 
by, as it were, angry flashes of silvery-greenish light, and it is to the coruscations in their 
aggregate condition of many millions of these minute organisms that the several phenomena 
above recounted are produced. 
One other characteristic manifestation of ocean phosphorescence dependent upon the 
presence in countless numbers of these minute animalcules may be recorded. To those 
accustomed to a seafaring life the spectacle is a common one, on nights when the luminosity 
is most in evidence, of fishes following or darting away from the sides of the vessel apparently 
aglow themselves with phosphoric light, and leaving behind them, in accordance with their 
size, a more or less conspicuous luminous path in 
the murky waters. It is commonly supposed that 
such form of luminosity is emitted by the fishes 
themselves ; but on closer investigation it will be 
found that this also is due to the presence of the 
animalcules under notice in countless numbers, 
which are disturbed into a sudden display of 
their phosphoric properties by the passage of the 
fishes through their midst. This light is reflected, 
as from a mirror, by the fishes’ glittering scales, 
while the Noctilucas continue scintillating for 
several seconds in the path or wake through 
which the fishes have passed. 
There are other animalcules nearly allied to 
Noctilucas which sometimes occur in such vast 
abundance in both salt and fresh water as to 
visibly affect its character. In addition to a very 
long lash they have a girdle of vibratile hairs. 
The fresh-water representatives of this group are 
sometimes brilliant green, at others bright scarlet. 
That instance among the Biblical Egyptian plagues 
These are the animalcules which chiejly produce marine 
phosphorescence 
Photo by IV. Saville-Kent., F.Z.S.J [_Milford-on-Sea 
SHELLS OF FORAMS HIGHLY MAGNIFIED 
The chalk cliffs of Dover and many other strata are matnly 
composed of similar microscopically minute shells 
