(39). It will surprise some of our readers to find that the Noctilucae, small as they are, feed upon Diatomaceae, and that in these microphagists we have the means of supplying our cabinets with specimens of some of the rarer forms. Colonel Baddeley observes that he finds that, when newly captured, each Noctiluca has several Diatoms in its interior, lying in the various chambers or pouches distributed through the body of the animal. These Diatoms all disappear in a few days, leaving nothing visible but the vacuoles or alimentary sacs filled with granular particles. A very careful examination shows an orifice near the tail or peduncle, the opening of which may be detected by carefully pressing it; and from this is protruded, by continuous gentle pressure, a very thin hyaline sac, filling gradually with fluid and small granular particles, till it attains about one-third of the size of the animal, when it bursts and disappears.

(40). The name Noctiluca is indicative of the extraordinary faculty that these little creatures possess of emitting a brilliant phosphorescent light. When a vase filled with sea-water containing them is placed in a dark chamber, the slightest agitation is sufficient to excite this phenomenon, and the smallest undulations upon the surface are indicated by luminous circles. On examining one of the animalcules attentively with the microscope, it is further observable that the light given out is not universally diffused through the substance of its body, but is confined to minute luminous points scattered here and there, which make their appearance in rapid succession and as suddenly vanish; so that evidently there is no special organ to which the luminous appearance can be referred, as in the case of the glow-worm and other phosphorescent creatures. In size these stars of ocean are almost microscopic, the largest of them not much exceeding the dimensions of a pin's head: but the amazing numbers in which they crowd the billows amply makes up for their minuteness; at certain seasons, indeed, it may be literally said that every drop of every wave contains one or more individuals belonging to the brilliant host.

On taking up at random a flask of sea-water, and allowing the little creatures to accumulate, as they always do when at rest, at the top, it will be seen that their bodies will form a stratum equalling in thickness from one-seventh to one-third part of the entire contents of the vessel. After such demonstration as this, it is easy to comprehend how the entire sea, rendered luminous by the presence of Noctilucae, seems to burn with phosphorescent fire. When the surface is tranquil in some well-sheltered bay, these living gems form a kind of cream of liquid light; or if a wave disperses their myriads and at the same time calls forth by agitation all their brightness, it is easy to imagine how a flame is thus evoked that spreads for miles, giving at a distance the appearance of a uniform sheet of light, but, when closely examined, resolvable, like the nebulae in the firmament, into constituent stars.

* Quarterly Journal of Microscopical Science, vol. v. p. 186. 1 Microscopical Journal, vol. iii. p. 203. 2 Rambles on the Devonshire Coast, p. 257.

(41). Amoebae

Yery nearly allied to the Bhizopods in their organization are certain minute gelatinous beings found in our fresh waters, which have long been puzzles to the microscopist, and a fruitful theme of discussion among naturalists (fig. 7.) These creatures appear under a good glass as minute patches of transparent jelly, having, under ordinary circumstances, a diameter of from 1/300-th to 1/600th of an inch, but remarkable for perpetually changing their form - at one time shrinking into the appearance of a little globe, then expanding into a flattened radiating disc, and again shooting out processes of their substance in various directions, so as to assume all sorts of shapes with the greatest facility, deserving well the names of Proteus and Amoeba bestowed upon them by zoologists.

Aniaba, showing the vacuoles in its sareodic substance, a, b, c, d, some of the various shapes which it assumes.

Fig. 7. Aniaba, showing the vacuoles in its sareodic substance, a, b, c, d, some of the various shapes which it assumes.

(42). When a drop of water containing these creatures is placed beneath the microscope, the observer at first discovers nothing but a few semitransparent or cloudy-looking motionless globules, from which flows, as from a drop of oil, a kind of semifluid stream, which, fixing itself upon the object-glass, seems to draw the entire mass slowly after it. In this way numerous expansions make their appearance from different parts of the body, which after spreading to a little distance again shrink and become completely blended with the central portion. The young Amoebae are perfectly diaphanous, and with difficulty perceptible except under favourable circumstances; but as they become older they lose this transparency in consequence of the accumulation of foreign particles in their interior, which seem to have been introduced from without by the simple pressure of the semifluid body of the animalcule as by the contractions and expansions of its various portions it crawls or rather flows over them.

Amoeba princeps (Ehr.), magnified 300 diameters. The figures 1, 2, 3 exhibit the same animal and its protean changes of form.

Fig. 8. Amoeba princeps (Ehr.), magnified 300 diameters. The figures 1, 2, 3 exhibit the same animal and its protean changes of form.

There are, however, other corpuscles or granules, besides those above indicated, found in the interior of these creatures. Some, extremely minute and irregular in their shape, appear to differ only in density from the surrounding glutinous substance, and these are considered by Dujardin to be rather products of secretion than ova. They move about, appearing to flow in accordance with the variable expansions of the creature which contains them. But besides these, in large specimens of Amoebae, other granules are met with (fig. 8,1,2,3), which on account of the uniformity of their appearance might with more plausibility be regarded as reproductive germs; but their nature is very doubtful. The Amoebae are capable of multiplication by spontaneous fissure, or by detaching a lobe from their bodies, which will continue to live upon its own account just as well as when forming a part of the original animalcule. On cutting one of these creatures in two, or tearing it to pieces, there is no escape of fluid perceptible; but each portion contracts itself, and commences a separate individuality.