CUP-SPONGES, PHOTOGRAPHED AS GROWING IN A CORAL-POOL.
The Neptune's cup Sponge, allied to this species, is sometimes 2 or 3 feet in height and diameter.
In lower forms of the infusorial animalcules one or more long, lash-like organs take the place of locomotive hairs. In this category are included the Collar-bearing Animalcules. Some of these build up tree-like growths by repeated sub-divisions and imperfect separation, after the manner of the bell-animalcules, while others excrete tubular dwelling-cases, inhabited by the resultants of the splitting process. Such forms can with difficulty be distinguished from skeletonless sponges.
The animalcule Noctiluca, which by its countless myriads is the chief constituent of ocean phosphorescence, is a member of the Lash-bearing group. This noteworthy form invites a somewhat more extended notice. It is to the presence of the Noctiluca in countless myriads upon the upper stratum of the water on calm summer nights that is especially due the diffused form of phosphorescence which is more essentially characteristic of temperate latitudes. Under the most favourable 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 transparent 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.
Photo by W. Saville-Kent, F.Z.S.] [Milford-on-Sea.
SHELLS OF FORAMS HIGHLY MAGNIFIED.
The chalk cliffs of Dover and many other strata are mainly composed of similar microscopically minute shells.
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.
